I'm on my second GTI import ! .... I've found no downside to it really ... only the lack of a 3rd year warranty
My current ED30, like yours, had a puncture repair kit (which I swapped with spacesaver from my part ex GTI)
Other things to check for UK spec are :
A. Full Spacesaver Sparewheel in boot - (UK Spec.)
B. Full Alarm and Immobiliser (check by locking someone in the car, keep still for a minute, and then move arms around ) - (UK Spec)
C. Headlight settings are UK spec (ie headlights are not always on with ignition)
D. 8 or 10 speakers (some Dutch imports have no rear speakers at all)
E. English Manuals in leatherbound GTi holder (UK Spec but rarely found in English with imports)
F. Check all the documentation (PDI stamped etc)
G. Find out how long it will take for the V5 form to arrive as you need this to register the car with VW UK.
H. Make sure it is a current year model - 3d type markings on indicator and light stalks are one sign.
The Service book should have the PDI stamped and dated by the foreign VW dealer - your warranty and VW Assist start from this date, so make sure it is fairly recent (a few weeks ago at most). There have been cases of 2 year old imports being sold as new

! - but not with ED30's as far as I know.
I have never had any problems insuring my cars, and never paid any extra premium at all.
Get it registered with VW UK asap after you receive the V5 (take the V5 & service book data sticker to your nearest VW dealer - they can do it)
You can get spacesavers on e-bay for around £50 if you're patient
Hope this helps..and enjoy your car ! you've got it at a great price, especially if that includes the metallic / pearlescent paint