Hi ColOfAbRiX
Sorry you are still having no luck. I know the milk you linked to - it's homogenised, unfortunately. Don't be fooled by all the 'organic' marketing. It's just pasteurised, homogenised, mass produced stuff.
It could be that more pressure will help you, but I am afraid I doubt it. The milk in the supermarkets here in the UK is probably the real issue.
There are only two supermarkets in the UK that I am aware of who sell unhomogenised milk. Tesco, which I linked to, and Waitrose. Waitrose sell it in 2L bottles, and it works out a bit cheaper. Tesco's is a pound a litre. It's also Jersey milk, so it has a nice high fat content - e.g. creamy.
I have heard people say many times that calcium chloride will reverse the effects of homogenisation, but it's never worked for me with supermarket milk here. I have tried making Mozzarella with supermarket, homogenised milk, and it was a disaster just like you describe - instead of forming a smooth mass, the cheese just crumbled like uncooked cauliflower.
I strongly advise you to try and find a Tesco or Waitrose so you can get truly unhomogised milk. Only the large ones stock it. The only other option, in my opinion, would be to try and find another source, like a farm which will sell it to you unhomogenised. But from your location (London) I am guessing that would be a challenge?