You won't be able won't get a good lifter from the cheaper servos as a good rule of thumb is about twice as much torque than is required to hold the other robot stationary. To have enough force left you would need a very short lifting arm meaning that you can't lift things very high and probably cant self right with it.

The other £240 servos will definitely have enough torque but I don't think you will want to have to buy another one after having it broken. I would suggest using really cheap servo board to make a giant servo with some relays like Mart (aka Rallikas) did for his RC car http://www.fightingrobots.co.uk/foru...p?f=240&t=3382.