Hi mate
The only compnay I know that actively does 7 day insurance is Norwich Union - they will sell you cover by the day now, which is quite cool.
Interestingly, if you get an HPI Check done by the HPI company for whatever they charge, they offer 7 days free insurance! Check small print for the jap import thing, but this may work out cheaper!
Dont know whether Norwich Union will cover Imports
JJ