Im in the same situation with another TOC.
However, having said that! There has never been a better time to wanting to be a driver. As trains get busier and busier, more routes gets electrified, lots of people nearing retirement, lots of people leaving the grade - things are quite promising.
Network Rail have already announced that they are planning to massively increase capacity around the UK over the next 5-15 years by resignalling and electrifying routes.
All you can say is that you have tried your best and now your 'next in line' for when a job does come up.
Don't forget it costs a TOC loads of money to screen and test applicants (they pay per person per test in the assessment centre) and I did hear somewhere it costs upto £500 per 'shortlisted' applicant with all the tests, managers interviews and medicals and things, so they obviously won't do all that for no good reason.