what are the first signs of a dodgy heart or heart attack

Pain in neck, chest, perspiring, loss of breath, tightening of the chest are symptoms of heart attack

all of the above plus a sense of doom ( l am not kidding, this is taught in first aid classes).
If you are in any doubt AT ALL then see a doctor

Probably when you keel over.

The classic symptoms are pain or pressure in the chest area, accompanied by shortness of breath, pain in the arms, especially the left.

Many women have different symptoms --nausea, general feeling of being tired.

The symptoms mentioned so far r the ''classic'' ones. If u believe u r experiencing one or more of them, then ur survival ''stopwatch'' has likely already been ticking for some time already. The important thing to take away from this blurb is this: If u conclude, based upon how u feel, that u r experiencing a heart attack, this is NOT the time to have ur sister drive u to the nearest ER as soon as she is done with her nails. This is the time to dial 911, tell the person that u r having a heart attack & that u need the ambulance unit best equipped to care for u en route to the best-equipped hospital. Every minute that ticks by when u r not being cared for by a professional team is one more minute closer to ur potential death. Today is ambulance personnel r trained & equipped to do things to help keep u alive on the way to the hospital -- things which ur sister or ur neighbor cannot do even if they know how -- they have to drive, after all. Also, unlike ur sister, the responding emergency unit will take u straight to the hospital most likely to be able to save ur life -- often, this will NOT be the closest hospital.
Finally, once u r at the hospital, if ur symptoms r NOT the classic symptoms described but u still have that feeling that u r in serious jeopardy, do not let the hospital try to discharge u with a bottle of Tums & a diagnosis of intestinal gas. You will always get the most thorough evaluation if u continue to insist that something is very wrong with ur heart -- patients who r wishy-washy about how bad they feel will get less attention in an overcrowded ER. One last rule of thumb -- all other things being equal, a patient who is wheeled into the hospital flat on their back on a gurney will ALWAYS seem in greater need than someone who walks in under their own power, or even someone in a wheelchair. Good luck.

Chest pain is the most important feature. Other symptoms could be undue perspiration, shortness of breath or jaw pain.