Re:
I cannot be certain it is not a Dave Lloyd, your pictures are not sharp and I cannot see any details of the tube joints.. but. There is a lug on the bottom bracket that the lower down tube passes into, all the frames Dave made had fillet brazed joints, and the Allsop era is when Dave was making rather than selling frames. Also, you have cleaned off the paint from the bottom bracket and not found a frame number, all of Dave's frames had a seven digit number starting LL, the next two numbers were the year of manufacture and the next three the individual frame number, so as an example his first ever frame was LL88001.
I know Dave had an Allsop frame in one of his catalogues, and I have seen one for sale but I have never come across a frame number in his register, so they are very rare. However, this does not make them valuable as if they were not popular when new, there is no reason to think they would be any more desirable now.
You have an unusual and interesting frame that could make a good project, but I am not sure it is anything more than that.