Emergency heart problems in the UK are generally dealt with via the NHS. If you think you may have a heart problem, especially if you may be suffering a heart attack, with heavy chest pressure associated with sweating, you should seek help as soon as possible either by dialling 999 and asking for an ambulance or if less severe via NHS Direct
NHS Direct: 111
If you have a heart rhythm disorder, and this has not yet been diagnosed for sure, it can be very helpful to attend your GP, a walk in Centre or you local A&E to get a 12 lead ECG. The heart specialist will find this very useful when advising later on your treatment.
I cannot provide a 24/7 service for my Private Patients. If you develop problems it is best to go though the channels described above.