vor

I'm not sure what ALS is. Do you mean ILS, i.e. the green feathers extending from the end of the runway on the moving map?? If so, most major airports have it, small GA airfields usually don't. To find out which ones do, just bring up your map and look for the green feathers, these indicate an ILS is present. 😉

Maybe I have the wrong terminoligy, what I am refering to is when you intercept the localiser the plane automatiacly turns to final approach and follows the glide path then before touchdown I turn of the auto pilot and land, it only happens at Heathrow when i try other airports it doesnt happen I thought it was called the Automatic landing system??? Roy

Looks like you mean ILS as you state you are turning the AP off before landing...therefore not autolanding. If the AP (autopilot) is coupled to the ILS it will guide you to the runway APP mode. There are several posts giving a full guide on how to best carry out an ILS approach.
Regarding autoland both airport and aircraft need to be properly equipped for this. ILS on the other hand is fairly common at most medium/large airports. Make sure you have the correct frequency tuned in and the correct rw heading selected in the course box.

As suggested plenty of posts about for how to set this up.

If you mean by ALS the Automatic Landing System, then this is a feature of the ILS in which the aircraft needs to be fully equipped. A lot of airports have an ILS as has already been said, but for an Autoland to take place, the aircraft needs to be equipped as the previous post said. Smaller aircraft don't have this feature - only modern airliners and it is only used in the correct conditions, i.e. near zero visibility.
You ask at the beginning how you know which airports have ALS (if you mean the Automatic Landing System, otherwise known as Autoland), but it is a question of whether the aircraft has Autoland rather than the runway in most cases 😉