I've noticed that the 'yesterday' channel is showing the series 'Tank Overhaul' at the moment - the paper decribed this as 'an awesomely specialist interest program'. I saw several of them a while ago when it was on one of the other channels - it really is close to tank nerd nirvana.
'Yesterday' is on freeview from 6am to 6pm only, but they seem to be showing it during the daytime so with a bit of strategic recording even those of us without Sky or some such should be able to catch them