WOW, what a nice lot of interesting replies and suggestions albeit we got slightly sidetracked into the Valve versus Solid State amplification debate. Whilst I agree with the remarks made on this subject I don't think it should be confused with the Analogue versus Digital issue.
In my humble opinion the Valve against SS subject is very much a 'Horses for Courses' thing and a matter of personal preference, both have their pros & cons, but analogue versus digital is much more clear cut. As I said in my original post I feel that vinyl versus CD is virtually 'no contest' at least in the mid to upper realms of equipment, it's more a case of getting CDs to sound as close as possible to vinyl whilst recognising you will never quite get there.
So, back to original issue, what are my options. Taking on board what you have all suggested it would seem sensible for me to try the softly-softly approach in ascending terms of ease and cost. In other words I think I will try interconnects first (not overly optimistic) then try to borrow a DAC (the Rega looks a strong possibility) before considering going the whole hog for a complete CDP change. Unfortunately I have to go quite some distance to my nearest dealer with a decent range of gear so don't want to be running to and from too often with various bits of kit. I would never, ever buy anything that I haven't heard in my own room by the way, as I believe that this is one of the biggest 'variables' in the way things can sound.
Who knows, I might end up realising that I can't achieve a significant improvement anyway but should I eventually get to the stage where I shout 'Eureka' I'll post back with results although I will probably keep posting with news of progess along the way.
Meantime, many thanks to you all for interest, comments and suggestions.