Leaking valve & change TRV

BB78

I've discovered this morning that my bedroom radiator has been leaking and the carpet is soaked!! I've got a Drayton RT212 TRV to the right and so am assuming the valve on the left is the lockshield. The water is coming from around the spindle. I've tried turning the nut & I've tried packing the spindle but I think the valve has had it and so I've had to turn the radiator off.
Looking on the net replacing the valve & TRV can be a DIY job but I really haven't got the time to give it a go myself. I wanted to replace the TRV with a chrome one anyway & they seemed to be priced around £20-£30. Can anyone recommend a decent brand? and can anyone give me an indication of a reasonable price to have someone in & replace the valve & TRV for me? Its a combi fed central heating system and I'm in West Sussex if it makes any difference?!
Thanks in advance!! :beer: