I would be interested to find where you got your information from, but I would like to clarify some of it:
I was one of those 3 controllers taken on in the last 3 years (2 years ago), and I validated my tower rating in 4 months. I am starting to cross train onto Radar now, the delay has been a lack of OJTIs as mentioned.
I can only comment for the last two years, where I have known of 2 other recruited controllers - 1 is still under training, the other left before validation.
The controller on "longish term sick" has returned to work and is now once again valid.
The "backlog" while I have been at the unit has never been greater than 3 controllers awaiting training - not sure if it has ever been as bad as five - but there again like I say I can only comment on the last 2-2.5 years.
One problem of attracting new controllers is indeed the money situation. Recently Liverpool advertised for ATCOs with wages upto £55600pa. DTVA top end is around £47000pa. The other issue I would guess is a lack of traffic - why would an ATCO move from a busier unit to a quieter one (on paper-not taking into account the amount of VFR transits Radar works in the summer months), unless they really wanted to be in the area; especially if that move also involved a pay-cut?
I can also confirm a previous post in which the airport had to close for ATCO breaks due to sickness. Most of the time we are able to cover it by coming in on overtime shifts, but a lot of that time we break SCRATCOH and it is something that obviously isn't a long term solution.
Big shame about the Heathrow numbers - especially with lower fares on the route (I believe they're still operating it as a low-cost service, although I may be mistaken?).
And of course today, with RVRs of less than 300m on both ends for most of the morning, nothing has landed - Newcastle getting the majority of diverted traffic
-HD-
*The views expressed in this post represent those of the author, and not those of DTV airport*