Tornado suffered a couple of fleet-wide crumps over the past decade, largely due to changes in the third-line (sorry, depth) maintenance arrangements while St Athan was dying a death and BAES was taking its time getting the line at Marham up to speed - which caused significant reductions in aircraft availability at certain points. Those were 'management' rather than 'aircraft' issues, and funnily enough, when the maintenance contract starting paying gainshare back to BAES, aircraft availability increased markedly!
The first-line serviceability of the old girl has steadily improved ever since GR4 came in. In recent years it's been driven onwards by some really good targeted analysis of the "standard" faults like outboard pylon snags, ECS failures and FOD-related engine rejections. There also used to be a bit of a culture of changing the easiest component in a failed system, inevitably followed after the subsequent crew-out by the next easiest, and so on.... that has all but disappeared now, with a big fault analysis project having shown what the culprit components usually are. The surprising thing is that the engineers are still learning stuff about it... you'd think after 30 years it would all be sorted! Perhaps we'll have it nailed for the retirement flypast so we can walk 16 for a 16-ship?!