Depending on how important a piece it is, you could try Artex in Landover: http://www.artexfas.com/

They do work for museums.

Our paintings needed restoration work and revarnishing, which was a lot more expensive than simple cleaning will be (if that is really all you need).

I have inherited a painting. I love it and it is in overall good condition but I think it could use a cleaning. There was a lot of smoking around this painting over the years. Does anybody have a recommendation for a good place to take it? If you've done this before, what did you end up paying? The painting is 4 feet across and 2 feet down. Thanks for any recommendations.