Just get on some free ones, most of the new boilers have common parts, usely electronics different find one that shows you about using multi meter Think Baxi do one , what's the boiler you fit most of ? quick chat with local rep, or just contact manufacture, or like most guys just ring technical if stuck,
Thats a downside of staying where I am, no courses hardly unless you travel. .
Get an old combi and convert it to lpg, and hook it up to a small lpg tank with one radiator and an outside tap ( hot ) in a garage ( up to regulatiions of course ) and voilla all the testing and practise you need , .you'll be surprised how quick u pick it up. Or just read forums or you tube lol