Rehabilitation for Rolo

Rolo is a 1 yr old GSD rescue in foster with me, he is the sweetest dog, he had a shetered start in life, spending most of it on the end of a chain, so he is like a big puppy and is just starting to enjoy what life has to offer.
He has been to the vet and physio and has nothing physically wrong with him regarding his legs but he has a serious lack of muscle behind. The muscle he is gaining is going to build up the wrong way if its left to devolop on its own, so he needs Hydrotherapy, twice a week to begin with for a block of 10 sessions, then hopefully he can go down to once a week.
10 sessions in a block is £350 but at the moment I'm paying more due to the fact he needs 2 handlers in the water, the team are hoping this will change after a few sessions.
Rolo is up for rehoming soon and it would be great to be able to support his on going therapy. 
I'm currently paying for this myself and will continue to do so but any support would be welcome!