WELL I FOUND HIM!!!

However it was by going through the images. I tried the tips that were offered - I don't use FindMyPast usually but didn't get any further at narrowing it down so decided to go in at the deep end. I opted to start at image 693 and work backwards - no idea why, just felt like it - and was rewarded at image 686. How lucky was I!!
I then tried to find him in the Summary book to see why I hadn't been able to locate him. He was in fact with his family and not lodging. The answer I found was a little worrying. The Schedule number was 343 however the summary books only showed entries up to 312 so no wonder he wouldn't show up! I have emailed ancestry to ask if the summary books are complete or a schedule has been misfiled somewhere.
My tip of the day from this is if an index tells you your person is in a particular RD SD and ED, then dive in and trawl the images and you may fall lucky as I did. Will let you know if I get a reply from ancestry.
Thanks for the tips on here for searching.