Independent dealer - worth getting car inspected?

I'm thinking about buying a '06 diesel golf in the North in the next week or so and am so far happy with it; it drove fine, cosmetically is ok and all the electrical stuff I tested was functioning ok. I don't know much about cars so that's as far as my opinion can go! It has fairly low mileage for a diesel (under 30k miles) and one previous owner according to the log book.

Usually I buy petrol and from main dealers so I'm (probably wrongly!) being more apprehensive about buying from an independent dealer. He's offering a 3 month warranty on top of which he said I can buy a warranty privately through an insurer or similar.

I have no reason not to take his word on any of this but the supposed issue of diesels in the North added to him not being a main dealer is making me wonder if I should cough up the £150 and get the RAC to look it over. The dealer said he'll HPI it for me.

Any thoughts? Thanks!