I expect their won't be any troops sent deep into Iran, we have a large enough stockpile of guided munitions to wage an air ops to completely eradicate Irans quest of becoming a nuclear nation. If anything we should use psy-ops to instigate a civil war instead.
Border conflicts however require feet on the ground, its possible after the bombing Iran may decide to do a fools rush with all the armor he has into Iraq, or let go all of his missiles into Israel.
Its what will trigger him off, I would say that if 300 or more troops were to suddenly HALO into Tehran he may cut and run and his next in command will surrender.
Britain should do what they did in WW2, make thousands of dummies and air drop them by chutes over Tehran, have a proximity grenade on each one.
After some thought I have to agree with Chuck Dent, Britain really doesn't have the capibility.
Using psy-ops to instigate a civil war is an intriging option, and one that might work since the last elections in Iran were a defeat for achmendinajad(sic)
B-52's loaded with live pigs on chutes.
Non-lethal weaponry.
Cheers!