hey ive got leak in my heater coolant is appearing on the gearbox tunnell, just wondering if anyone has had this problem, as in, is there a common cause? thought itd be easier to ask than go through it all bymyself.

The water control valves sometimes leak & are readily visible inside the car, so grab a torch & have a look at this.

Next in line are original heater hoses. Age shall not weary our departed young soldiers, but it does weary old coolant hoses, so while you are down there, have a look at these. There is one inside the car & two that pass out into the engine bay.
I recently bought all three of them new from my dealer, so they are still available, even if they need to be ordered in.

If these all pass the test, then it will be necessary to pull the whole heater out & have the core checked, tested & repaired as necessary.

thanks dodgeman as always your long indepth replies have pointed me in the right direction....