Your best bet is to contact a chap called John Marshall-East through the Lincolnshire Aviation Heritage Centre website (which I haven't got the link for) as he is responsible for the Brian Nicholls Hampden Project.
A great project but the Hampden panel is very difficult to get the correct instruments for or when you can find them such as the fuel gauges these are very expensive as they are usually sold as Spitfire ones.
Can you give me a ball park price on the fuel guages? I've got a line on the panel dimensions(I hope). By the way...I love your Halifax panel! I could only dream of a Whitley panel. I need the dimensions and instrument markings and numbers. :-)
The large fuelgauges can be between 100 and 150 pounds each and you would need three. As they are mostly sold as Spitfire gauges they are very expensive. This is just an estimation perhaps e-bay can help out.