depends what your current tax status is mate. Those of us that work offshore are registered that way (with either UK domicile or expat status). That means we work to the '90 day rule' ie you can only spend 90 DAYS in the uk or you are liable for tax-even if you earned it all offshore. Yes. The taxman is a tosser. Going by the book you'll have to declare your earnings in your tax return (unles you are going as an employee which it doesn't sound like it) Is this a UK company you're going with or a foreign one? That all depends who you'll be invoicing as some UK companies will stiff you (one old & well known one even takes PAYE off you despite most being registered as self-employed).
One way of making up the 9 months is to make sure you're out of the UK for that time. There are small ways of clawing back days-arrive in UK on a friday & your'e not counted back in country until the monday. Keep a record cos if they pull you they'll go through your arrse with a toothcomb. haven't been unlucky enough to have that but know enough that have-doesn't sound good.