I thought I would post an update in case it helps somebody else out in the future.
I changed Alfie on to a raw food diet. I started with feeding him 3% of his ideal body weight each day but he lost weight so he's now getting 4% and I'm watching him closely as I don't want him to lose any more. We're using Nutriment and he's really enjoying the food. The best part for me is that he doesn't smell anymore. He also has a lot less "output". I'm so happy that this problem appears to be solved. I'm off now to read up on feeding a raw diet that isn't prepared so that I can just visit the butcher when we go away on holiday and I don't have a freezer available for his food.
Nice to hear that Alfie likes his raw and is more fragrant

My two are raw fed and one of the first things I noticed when I changed them is that they don't smell doggy (Louis still smells of pee but that's because he hops along while cocking his leg and sprinkles himself sometimes)

I always have a tray or two of Naturediet or Forthglade in the house for when I forget to thaw out their raw or go shopping for it. Thought I'd mention that because it might be a useful standby when you go on holiday.