It's good news. I have agreed and now received a partial refund of £45 from the seller, meaning the Speeder Bike has now cost me £70, which for one in this condition I am happy to pay, as it genuinely is a great piece, it just wasn't as advertised.
The seller couldn't have been better about the situation. I politely explained the problem, and they apologised immediately, accepting the facts with good grace and offering the partial refund (I had said I would be willing to return it for a full refund, but would also accept a partial, and gave the seller the choice). I genuinely do believe the seller made an honest mistake in the listing and that no deliberate deception was intended, but even so, until you contact a seller in these sort of situations, you never know how they will react. I am very pleased to say that this gentleman could not have been better about the whole thing.
All's well that ends well! :-D