You'll be fine flying your N reg in the UK and Europe, including IFR. I'm not 100% sure about the import duties but I would have thought that this would not be an issue if you are a US citizen? Someone will probably correct me on this.
Be prepared for a really different flying environment. Very high fuel prices, expensive hangarage if at the larger airfields, landing fees whereever you fly and chargeable instrument approaches. Maintenance will cost more than the USA and insurance will cost more if insured using UK companies.
Where will you be living?