OK, I know I said I wouldn't do it but......
well after much persuading and with help and advice from Dark Mantis, Aussie Allan (Thanks to both of you for this) & hours of research on the internet I have finally bitten the bullet and gone down the water cooling route.
BEFORE:
With the Noctua NH-D14, which has proven to be an excellent Air Cooler and has given me some really remarkable O/C results with both AMD and my Intel rig.
AFTER:
Now, there's not really a lot my space inside my case which is the NZXT Tempest Evo, so I did have to dig out a chainsaw (good piece of advice from DM here!) to do a little modification but no one said it would be easy.
ALL LIT UP AND PRETTY!
And now the system is up and running. Already, I have noticed that things are much cooler and I have my i5 2500k humming along at 4.6GHz with the CPU showing 27C (down from nearly 40C on air) at idle and up to around 40C under full load (further testing needed to qualify this result) with the room showing an ambient temperature of 22C. Now hopefully, I will be able to break the 5.2GHz I got with the Noctua Cooler.
The system is now a bit quieter than before, although I do find the occasional gurgle of water, passing through the reservoir, a little disconcerting.
For those who are interested, the main water cooling components in this build are:
XSPC RayStorm CPU Block
XSPC Single Bay Reservoir
Laing D5 Vario 12V Pump (running at setting 3 at the present)
Koolanc Laing D5 Pump Top
Phobya G-Changer 360mm Radiator
13-16mm (1/2") Tubing