Advice needed on 403 fuel tank cleaning

[mikebro]

I've just got the fuel tank out of the 403. After a period of indecision, the decision to remove it was made when one of the tank sender unit screwheads had to be butchered, leaving the remains firmly in the tank aperture. That's all fixed now, but having got the tank out, there is a fair amount of hardened petrol products in there (some stuck firmly to bottom of tank, some floating around) that I need to remove. Anyone have first hand experience of a good method? The tank is aluminium of course.

Thanks in advance.....

Mike Brooks