I would be very wary about who you get to do any case colouring. Unless they know what they are doing the colours will not be traditional "English" and your Hollis will look wrong. But, wose than that is the liklihood of warping the action, requiring expensive re-fitting.

The best work is still done in the UK (Birmigham), but the guy prefers to work through other gunsmiths, so I won't give his details - the dealer that you bought the Hollis from should be able point you in the right direction.

If you are prepared to send it out of the country, there is a gunsmith here in Melbourne, Australia that is doing quite good work. PM me if you are interested and I will give you his details.