Well, obviously it is "worth it" if that's what you, as the successful bidder, have committed to paying for it. It's a good price, if that's what you're asking, I paid £135 for a decent second hand one a few months ago.

Of course, it is what it is... they offer to include a compatible charger but they don't warrant that it'll be a 1200mA Nokia AC-10X, the photo shows a UK keyboard, but the listing doesn't guarantee that it's a UK model. Yo also have no guarantee you won't get hit for customs charges and VAT on it, as it's a commercial purchase from abroad, worth over £18.

Whether it's "worth it" is subjective, I bought my first N900 from Vodafone on contract, and my spare one, second hand, from someone else who'd done the same. I personally only regard the hassle of importing as worth it for items that are small enough to drop through the letter box, cheap enough that they legally don't attract VAT and duty (that means below £18, in the UK). and inconsequential enough that if it screws up I'll chalk it up to experience rather than expect to send the item back.

But, you've bought it, and you've bought it at a good price for what it claims to be. If if turns out not to be, well that's a risk that you've chosen to take.

I have a brand new boxed N900 which i think im gonna put on ebay soon, any ideas what sort of reserve i should put on it?? I would be gutted if it went for a low price!

That's anybody's guess; you could try searching completed listings (needs you to be logged in) for an idea of the prices at which they're successfully selling.

Off the top of my head - and this is a few months old - there were many "barely used" at £150-£160 buy it now - which I was trying to avoid paying - and I jumped at £135 for one with a credible seller and a credible month's usage. I don't know what current prices are, but I suspect that you'll easily get £150 for it, but you'll struggle for £200. My advice would be try a Buy It Now at about £180 and be prepared to reduce to £150 if it doesn't sell. You'll probably get less at auction.

I bought my n900 from that same guy and it was refurbished, but he always tries to sell them as new.
I have bought 3 cellphones from him, 2 of them I am sure were refurbished, 1 of them is hard to know.