Diane
British Airways fly direct to Tel Aviv from Manchester. It's a great country to go to.
I believe you would still be able to the "JY holidays" but book your own flights - I'm sure the customer services would be able to confirm/advise on this. When I did Israel, there were people who flew from Manchester & Cypus.
Jaya
Hope you have a good time. Just a forewarning, I flew from Heathrow. Before checking in, you get asked questions by security. I got a bit of a grilling because I had a Syrian stamp in my passport.
Anna