I know its much too late now but it could help other users out.
You could try Axon Components in Leeds, I have used them a couple of times. They seem to have quite a large selection of switches and some switch tops.
they're at http://www.axoncomponents.com
If they do not have the switches you need, then I would second the recommendation and suggest EC Smith, at http://www.ecs-marine-equipment.co.uk