Trying to get into Laira is one of the most sought after jobs in Plymouth, like you said because of the pay, & job prospects. Yes, they rarely advertise, as basically as soon as a job becomes available, the staff usually spread the word themselves. So, unless you know someone who works there, or someone who has connections with Laira, it's pretty much a long shot trying to get into there. Believe me, I would love to work there if I had the chance, just a case of being in the right place at the right time, & keeping your ears open. Also, what you need to bear in mind, Laira is one of the 'specialist' depots (the other 2 being Bristol St. Phillips Marsh, & Old Oak Common). This means most major overhauls of the HST fleet is done between the 3 depots, what can't be done is contracted out. This is why jobs are highly sought after.
Mart