Thank you Muzzer and yngndrw for your assistance. I ordered the 250NM strut in 6/15 size and 220mm extended length (centre of cup to centre of cup) and it fit perfectly. I also ordered 8mm metal ball cups and the strut came with 10mm plastic cups but I found the plastic ones fit a lot easier and still clamp on well. Very pleased and hope this helps someone else in future.

Attachment 32549

Attachment 32550

Cheers

Andrew