> I just bagged what seems to be a bargain Japenese Squire Strat on Ebay via buy now for 150.

When you use Buy Now without asking the questions beforehand, you take a big risk, which you need to follow through, no matter whatunless the description is erroneous.

> What i'm slightly concerned about is that it has a Fender 'F' neckplate which the seller rightly states is unusual.

Its not uncommon for any guitar to be upgraded, which can be minor or major, and things like Fender 'F' neckplates for Squiers are par for the course.

> the serial number is on the headstock (QO24243)

If its MIJ that makes it 1993-94, whereas, a CIJ would be a 2002-03 model. So, I would assume its the former. Neither is vintage or in any way desirable.

> the body could be any cheap strat copy

A Q Squier is a cheap copy, and the body is most likely plywood.

> is their anything the seller can look for to identify the body or parts as a genuine Jap Squire in order to reassure me before he posts it?

Not really! The body may have a red EX or EXP stamp in the neck pocket. But, as the body would most likely be plywood anyway, IMO a replacement body could only be an improvement.