Told by vet to change his diet, help?

[Emmurz]

My poor little fella is really unwell at the moment, he's been passing lots of blood in his urine just lately and seems to drink only when he's on the brink of dehydration.
We took him to the vets yesterday and we were given some medicine to give him (Baytril but differently concentrated to what he had before) and some medicine for dogs that will ease his pain and work as an anti-inflamatory(Metacam? I think.. I'm unsure as my partner is looking after him whilst i'm on holiday)
However he said it would be best to change his diet and to take him completely off what he's eating now (Pets at home Muesli) as he may be picking and choosing his food and not getting enough nutrients.
He suggested getting an all in one food mix or pellets but i'm unsure as to what's suitable or what makes I can buy.
Any suggestions and where I could get them from would be a great help!
Also how would I go about changing him from his Muesli to another food? I know roughly that you have to introduce it slowly but still would like to know exactly.
Thanks in advance.

[souffle]

Oh dear poor wee chomp. I'm not sure he will eat a change of food but you could try supplementing his food with an all in one. The only one I know is Supreme selective which is like little hearts and tastes like ryvita. Ours liked it at first as a treat then they just ignored it. It is here
http://www.pet-supermarket.co.uk/erol.html#1X0
It's contents do not seem very much and though nutritionally sound to my mind it does not challange a hamsters natural behaviors of foraging and shelling seeds etc. Few hamsters will eat an unbalanced diet overall and it sounds more like your wee man is just suffering from the illness rather than malnutrition. Bunny foods (this is a hamster food) make a rice flake supplement for ill hamsters called Rice flakes and vegetables health food. You can get it mail order from Rondetto International on 01525 280770. They also do a hamster food which may be worth a try
www.bunny-nature.co.uk (the website isn't working properly just now!)
also the food is here but the special rice flakes don't seem to be. There are also other foods here
http://www.zooplus.co.uk/shop/rodents/food/hamster_food
To change over you need to just start adding a small amount of the new food to the old and each day you feed increase the amount. I'd say do it over a 10 day period.