Hi - thanks for your patience through this. This is the meter I bought:
https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1
I attach a photo showing the frequency specs. Let me know if it won't do the job and I'll ask around to borrow a scope.
I'll get the motherboard out today and give it a better clean as per the messages above. I have a chip puller so I'll pull them out as suggested and examine them.
Thanks again.