I doubt that one could muster an armoured element for an overseas deployment like we've seen during Op Telic with some 200+ active tanks.
An Armoured Brigade with 56 MBTs and 84 IFVs is more of a MechInf Brigade with another name and defenitely on the lower limit of an effective mobile ground combat element. As good and important light infantry like Paras and Royal Marines are, they lack protection, persistence, mobility and firepower for anything more than assaults on ill equipped and training and rather static enemies (excluding difficult terrain like urban areas, heavy mountains, etc.)
I don't get how the idea of heavy forces being only a sideshow took hold in some circles. In the past 20 years MBTs were the premier UK ground combat element during to big conventional wars (ODS and OIF) and played an important supporting role during the assymetric phase of Iraq and Afghanistan with UK forces gettig MBT support by the Danish and Canadian battlegroups.
The same applies to the US with the USMC getting them to Afghanistan.
Just imagine Lybia would have progressed into a ground campaign (not all that far fetched a possibility). The mission of going after Gaddhafis troops further than just holding Bengazi would have fallen to armoured/mechanized formations.
Three to four companies (or squadrons...
) of MBTs won't give you mich of a frontline with the need to rotate units in and out of combat.
I don't even want to start to think about a real conventional war against an even halfway competent enemy (cough...Russians...cough). When a badly mauled battalion (or Regiment...
) of tanks means you loose roughly a quarter of your maximum active combat strength than our whole idea of a serious conventional option is rather questionable.