Am going to stick the fan the other way up so it's blowing through the heat sink and straight into a top case exhaust fan. Will reseat the whole thing on Saturday or Sunday and will fill the gaps then. Will get some cling film and try that approach for applying the MX-3. Not rushing as a) It's running fine after an overnight stress test with a gentle (multiplier only) overclock and b) my new GPU has just turned up and I'm itching to try it out.