No point in me asking peoples opinions here if I don't at least consider what's being said to me .
Just thought I'd update this, got the car repaired in the end at an independent garage which seem good. Cost just over £200 in all, for the coilpacks / spark plugs, service and the other niggling issues including boot fixed.
A lot cheaper than anywhere else seemed to be suggesting.
Glad I didn't flog the car now, a lot cheaper than trying to upgrade car (which would probably have been a downsizing) and even if I do change car I can probably flog it for more than I was being offered now .