Looking around the sources on the web, UK is hoping to to have a single armoured Division available C.2020-25.
This Division will be comprised of two regiments of Challanger 2 tanks each with three squadrons of 18 MBT and a recce squadron with Ajax.
One armoured recce regiment with three squadrons of 14 Ajax and one support squadron with Ares APC's etc.
Four Armoured infantry battalions each with three companies of 14 Warrior 2000 IFV plus one support company with 8 SP mortar vehicles, 8 Ajax, etc.
Two heavy Protected Infantry battalions each with three companies of 14 Boxer APC and one support company.
This force will be supported by AS90 155mm SP Guns and Multiple Launch Rocket Systems, NLOS Spike and at least one squadron of dedicated Apache attack helicopters. The aim is that this division will be deployable at under six months notice, with the first brigade available at well under three months notice.
Total British MBT strength, including reserves, will be less than 250 vehicles, including only two front line regiments. Total British Warrior 2000 IFV strength, including reserves, will be up to a maximum of 450 vehicles (everything I have read makes me think this estimate is decidedly on the large size).
In addition UK will have two 'rapid reaction' Strike Brigades each of two or three (unclear yet) heavy protected infantry battalions each with three companies and a support company presumably with Boxer APC and one Armoured recce regiment with Ajax, supported with 105mm Light Guns, etc.
The main actual rapid reaction force will remain the Air Assault Brigade with two Parachute battalions and up to four squadrons of Apache Attack Helicopters (The British Army Air Corps has six squadrons of Apache attack Helos, one of of them an operational training unit) backed by two light infantry battalions one in the helicopter assault role, 105mm light guns, etc, etc. At 8,000 men this brigade can move very quickly anywhere in the world.
In theory -and in practice if the RAF is not too busy- UK can para drop a whole para battalion, but such operations are pretty rare now and given the size of the RAF transport fleet it is fairly unlikely that UK would ever actually operationally para drop much more than a company or so.
One other British parachute battalion is normally tasked with Special Forces support, providing base protection and other 'heavy' support to the SAS, etc (a large proportion of SAS soldiers come from the Parachute Regiment). One reason UK is keeping some Hercules C-130 aircraft, after Atlas comes into service is that the SAS do not like the larger Atlas for covert drops.
In addition there will be one armoured infantry battalion with warrior 2000, assorted light role battalions (some with light protected armour) in UK, and garrisons, such as those on the Falkland Islands, Brunei in the Far East and the Crown Bases on Cyprus, etc. There is normally one British light role battalion in Africa doing training, etc.
Reserve Forces (the former Territorial Army) will provide 30,000 or so extra troops (the aim is almost 40,000, but actual recruitment is below that) including a reserve MBT regiment and some light recce forces, etc, all of which, unlike the old TA, can be deployed overseas without a major national emergency.
There is also, of course, the Royal Marine Commando Brigade with three battalion sized Commandos and supporting forces including 18 105mm light guns, helicopters, etc, including the SBS, the Royal Navy equivalent of the USN SEALS and part of UK Special Forces (but they are part of the Navy, rather than the Army).
Weaknesses in the British land forces: Weakness in the Royal Navy, especially in Destroyers and Frigates (down to just 19 now compared with over 60 in 1982) due to Government neglect, for an Island Nation totally dependent on the sea for trade, imports and exports
. You can move relatively small and light forces by air providing you have air superiority, but major land forces get moved by sea. You need carriers for air cover, helicopter carriers and landing ships for Amphibious mobility, Frigates for anti submarine and surface defence, and Destroyers for air and surface defence. Hunter-killer subs to sink or scare off enemy warships, etc.
Lacking these your military cannot go anywhere it cannot drive. Think Hitler and the large, highly professional German forces and the total lack of any chance of success of 'Sealion' against UK in 1940. Now compare that with the success of D-Day in Normandy in 1944 and the Allied land forces that were still not really a match for the best German units in 1944. The difference was a highly professional and powerful Allied naval force. Air Forces are vital -and Carriers give you those with mobile, protected airfields- but air forces alone cannot win.
The 'Strike Brigades' as they stand now, are a bit of a mess. Very difficult to see how you integrate tracked 40 ton Ajax with wheeled Boxer APC's. Since the advantage of wheeled, as opposed to tracked, forces is strategic mobility...
Lack of area SAMS (Rapier lacks range and is getting very long in the tooth) lack of wheeled SP gun support for the Strike Brigades. Lack of ATGM support under armour (ie fitted on an IFV and/or APC) although some or all of these may be addressed in due course. Above all it lacks 'depth' in that the front line forces are in no way easily replaceable, although this latter has almost always been true of the British Army outside the two World Wars.
By the standards of any Western nation, other than the USA, it is, or will be, an impressive enough force, with the huge advantage of lots of combat experience, close interoperability with our Allies, especially the USA, and that it can be moved and used outside Europe if need be. The UK Royal Navy ability to operate large Carriers from C.2019 onwards, together with the UK Amphibious force, will also hugely strengthen its reach and punch.
Hope people find this useful. UPDATED 22/12/16