Do DAS. Get it out the way imo.

Depends on the type of bike you want, if you are looking for a sportsbike any of the current crop of jap 600's are excellent choices. go sit on a few, see which ones you prefer

As for insurance, forget about fully comp but unless you live in Beruit I would have expected to pay in the region of 6-700 quid for my first year on a 600?

What sort of quotes have you been getting?

Try www.ebikeinsurance.co.uk or www.bennetts.co.uk