Hot starting

[listernoble]

I have a 1969 Imp engined Ginetta G 17 single seater running twin 40's, which I use soley for hillclimbs.
Starts first time from cold but when hot is a so and so to start on button, but fires up first time from a bump start.
I know the battery is OK and anyway the same happens if I try a larger battery with jump leads.
The carbs sit very closely on top of exhaust,the exhaust is heat wrapped and there is no room for an alloy plate etc.
I do not want to chop the manifolds about as the car runs in historic class.
Previous owners say they always had this problem,although when I had it on the rollers recently it started easily with min throttle.
I assume it is hot or boiling fuel.
Any ideas on how to start ?
Lister