I had supported a ticket to PMDG about the issue, but considering the volume of support tickets they must be going through right now, I decided to go ahead with a complete reinstall anyway. I agree, a reinstall for one aircraft is pretty time consuming, but I've been long overdue a cleanout and reinstall on my installation of coming up to 4 years. But I appreciate that this is not the case with everyones install!
Anyway, for anyone else having this problem, I have reinstalled everything and my FSX no longer crashes when loading the T7, so can only presume it was conflicting with something in my old install! If you're desperate to get it to run and have plenty of time on your hands, its the way to go!