Hi Brucey & everyone else who kindly posted replies,
I just wanted to say thanks again for all of your help & tips on the issues that I had with my rear axle/hub!
Long story short but because of holiday and then illness in the family I'd not been able to touch my bike for a few weeks until last night.
Anyway over time I had numerous attempts at taking apart the rear hub and then reassembling which never resulted in a wheel which was running freely. Anyway I persevered and continued to disassemble and reassemble over and over so I've had lots of practice and taking the hub apart now.
Finally I got it to a stage whereby it's all pretty much sorted and I rode to work this morning with no problems. The first few revolutions of pedaling were a bit odd because it felt like I was pedaling with getting forward motion as something slipped but then I realised that this sensation was the freewheel tightening itself.
With the wheel there is a tiny bit of play/wobble from side to side but it's only really slight but I didn't want to tighten the cones anymore because it seemed to be at a point whereby if they were tightened any further the axle wouldn't turn smoothly.
Given the frankenstein assembly of what seems like various mismatched parts on this bike that I bought secondhand I don't think that the result I have is a perfect as if new result. However it seems to be good enough to keep the bike going for now. This result is good enough given that I'm saving towards a new bike and didn't want to have to spend too much on new wheels to repair this bike. In the end I got the job done for under £20.
Just in case anybody else has hub issues this video link posted by milkonesugar was really helpful if you need to overhaul the hub and have a freewheel like I did (once I finally clicked and got the difference between a cassette and freewheel).
https://youtu.be/_axwV6sfaAsI'm sure that somebody who knew what they were doing could have diagnosed the problem and fixed everything in under half an hour. For me it took a lot longer and it was try and try again but I'm glad that I persevered and feel like I've learned something as I start from scratch in trying to learn how to maintain my own bike as opposed to always having to take it to a mechanic.
Cheers,
John