I wasn't going to post this initially, as it wasn't the outcome I was hoping for, but very, very sadly Bernard has left me and has had to go back to Wood Green
I know that there will be some who will disagree with my actions, but I feel totally justified in my decision. I am satisfied that I did everything that I could to help him settle in since we moved house in July - but he just wouldn't / couldn't.

I have no idea why. As you know, I even had a cat behaviourist to come and visit him and make an assessment, I followed all her instructions and even though they seemed to work at first - ultimately his behaviour got worse instead of better and I was sacrifcing the wellbeing of the other cats for him.
The final straw was when he attacked Lily for no reason whatsoever, totally unprovoked. Lily is the calmest and gentlest of them all and she literally didn't know what to do. I had to scruff Bernard to pull him off her.
It's been an incredibly hard decision and not one that i have taken lightly, but he has gone back to Wood Green (which is a bit of a killer in itself as I know he didn't like it there the first time around) and is getting lots of love, cuddles and grooming from the girls there. He's settled in quite well and they are hopeful that it won't be long before he is reserved - as he's soooooooooooo handsome.
I love Bernard very much and I wish more than anything that I could have got to the bottom of his problem. I hope that he will find a wonderful forever home now, where he can be the only cat and live out the rest of his days in peace.