Sorry I haven't been on any sooner to let you all know an update!
Hammy had all his medicine and it didn't look good after a week. He lost over 15g of weight and was still toppling over.
However, I didn't feel as if he should be put to sleep so I let him do what he wanted. He slept most of the day and I gave him water through a syringe for around a week and a half and gave him a range of food such as carrots, wet cereal, breakfast oak biscuits and anything he seemed to want to eat. I know this probably wasn't the best idea giving him everything he wanted but when he lost weight I thought that giving him anything would be better than nothing.
I weigh him every day and last week he seemed to lose weight almost every night (about 2g). This could just be due to changes that are normal but the lowest he went was 106g and he was 125g when we took him to the vets as told above.
Hammy has been out tonight and he's walking so much better than he has been. He is going quite fast and I can hardly catch him when he goes for it! He's also + 6g from last nights weigh in
He's also managing to empty his cheeks out himself and he's also going for water himself now from his bottle.
It's a good sign he could be getting back to normal, even if he is old!