Well, I'm impressed!
Basically we came to the conculsion that Jess has no confidence at all. We spent 3 hours with the behaviourist at home and she main thing she recommended was having a litter tray uncovered (no lid) with no liners or newspaper just next to the tray he normally uses. And then have the upstairs tray with just catsan and no liners or newspapers. We also need to try another litter as the catsan is quite rough on his paws.
Also recommended was feeding smaller amounts and often, which we can do but unfortunately we can't leave food down whilst we're not there as Jess will gobble the lot which we can't allow whilst his on the urinary food. So now we're feeding 1 third of a pouch every 2 hours in the evening. And in the morning half a pouch every 2 hours.
We're also going to get a bigger cat tree so Jess can climb and raise himself up.
She thinks Jess might have some orinental in him as his so big but with a slender face, and the way his so particular.
One thing she did suggest was possibly having a confort zone and seperating Jess and Milo but I won't allow this to be honest, I don't feel its fair and I don't want to undo any of the hard work we've done of the past 3 months to get them to get on. She did agree though that having Milo has benefited Jess greatly as his body language was showing more confidence (showed her 100's of pics of before and after).
So far we've came to the conslusion that the trigger was us going on holiday and Jess being left 17 nights, then us putting the chrismas decorations up, plus (and its something we never thought of) the arrival of 2 new dogs in our road, one next door and one next door but one. All this combined basically knocked him over the edge. I also have to be careful what smells I bring into the house from the office dogs at work as this might not be helping.
The most amazing thing is that we did what she suggested with the litter tray (no lid, no newspaper, no liner) and Jess has been weeing in it, not only that but yesterday he had 4 wees in 24 hours, never ever has Jess wee'd 4 times in 24 hours so we are thrilled already.
Anyway I just thought i'd update you all