Hi Everyone. Can You Help.?

[TwoTankAmin]

Not knowing about meds in the UK can't suggest anything. To me it is perfectly clear what happened. Adding a fish 12 hours after arriving from Asia did it. You put the problem into the tank with it. This fish needed to be Quarantined for at least a month if not more.
 
DO NOT ADD ANY MORE FISH!!!
 
Then here is a list of disease sites, hopefully they might help you diagnose the problem:
http/www.fishdoc.co.uk/
http/animal-world.com/encyclo/fresh/information/Diseases.htm
http/badmanstropicalfish.com/fish_palace/tropicalfish_disease_identification.html