Here's a couple more from my Dad; the first is useful for Pentax owners, whilst the second useful if you want a lens re-coated:

Harrow Technical - Pentax
020 8938 4660
http://www.harrowtechnical.co.uk/

Does a decent job for a reasonable price [see website for details]
Can take from 10 days to 3 or 4 weeks depending on work load

Recommend? If you want a straight forward service - Yes.
Otherwise note carefully everything you want done and he will give an estimate.

Optical Instruments (Balham)
020 8664 9799
http://www.optil.co.uk/

Not had enough back from them to make a clear judgement.
Took in a 50mm f1.2 Canon ltm and a collapsible Summicron for re-coating, which also jammed when I tried to extend it.
The Canon is still there along with 2 Canonflex lenses in for a general service.
They also re-silver things like prisms and range finders and I think mirrors

Polishing and re-coating - excellent

These people are very busy so anything you send them will be gone for a loooong time.
Be aware that TLRs cost more [2 lenses] - new coating on 1 lens and old coating on the other looks very odd when the time comes to sell it.
They will do it though, if you want them to.

They don't take cards, so if you go in person take cash, or post a cheque.