Dear Malcolm
Thank you for your help and kind offer. I had a few moments to look at the enlarger this morning....the diameter of the hole below where the neg carrier should fit is about 75mm but it was difficult to measure. The whole is circular but with a square imposed upon it that appears to overlap the circumference slightly . please follow link to a)diagram of the carrier (off packaging seen on google...) for a different format b)photo of where carrier is to fit and c)photo of where carrier is to fit with condenser in down/lock position to hold carrier still.
[/URL]
If you cannot view the pics let me know and I will e-mail to them to you.
In case you do have one....please send it to me David Healey at King Edward VI Handsworth School, Rose Hill Road, Birmingham B21 9AR
Best wishes