Andy,
The TT has no provision for "tick over."
However, there has been some discussion on Brit Bike Forum about GP carbys on Spitfires and a modification to the slide which allows tick over. It involves drilling a very small hole in the side of the slide, on the cylinder head side, from memory.
This should work OK on the TT.
As to the hard starting, are you sure that it is a carburetor problem?
If he really wants to fit a Monobloc, have a look at the Super Rocket specs.
Trev.