Who makes a VP M700R Freehub??

In my experience the symptoms you describe are more likely to be in the chain and / or derailleur, especially the back pedalling problem. Freehub designs vary widely and it's difficult to know how to get a specific one off. This is where a proper bike shop will earn its crust, but if you can't get the bike booked in... here's what I would do:

1) clean the chain and re lube, moving every link to find any that are tight. May be time for new chain.

2) clean cassette and derailleur until really sparkling.

3) test back pedalling again with smallest sprocket & largest chain ring selected and hence hopefully all the tension out of the rear gear cable. If your limit screw is correct and so the chain is nicely in gear, but you still have grumbling back pedalling, check that the derailleur cage is hanging vertically - if not, something is bent.

4) you can bend things back straight if v careful but you are into bike shop territory really. A good one (not most Halfords branches) will have the tools to diagnose and fix this. The hanger (bit of metal between frame and derailleur) is designed to bend if the bike is dropped as it's cheaper to replace. A good bike shop will have the ability to straighten or replace.

5) if nothing is bent, index the gears (YouTube).

6) if after all this, it's still bad and you suspect the freehub, can you borrow a known ok wheel to help eliminate? The main issue tends to be broken or gummed up pawls, and this gives either no drive at all or a distinct clunk when starting to pedal after coasting.

7) if after all this, the bike shop is still not an option, consider buying another wheel. I have a spare rear wheel for exactly this reason: the freehub failed (broken pawl) and the parts took ages to arrive at the LBS. In the end, for a low end wheel, replacement at the start would have been about the same cost, and now I have a spare so I can swap for different tyre choices and when the hubs need doing...

Hope this helps a bit.