To get through class 2 will cost at least £1500 with all costs to get the license provided you pass first time.
I too am looking for a change of career in Sheffield/ Chesterfield area but was highly surprised at the pay rates for class 2. Even class 1 wages raised an eyebrow. I’m on 37 hours at £11.50 an hour / £17.50 over 37 hours for overtime. After my 8 hour shift I leave. What I’m trying to get across is the grass isn’t always greener. Wages for driving are lagging behind. Add on to a 12 hour shift your commute time and you could be looking at a 14 hour day for a little more you are getting now. Add to the uncertainty of the job market and agency work with no secure work to build up your experience.
But in the end you have to be happy as life is too short. I would take your class 2 on weekend off/week off and still keep your old job. In your holidays apply to agencies to build experience. Then wait until the ideal job comes along. Check out Peter Smythe training. There are jobs for class 2 paying £11 an hour but you will struggle to hit the £2k mark.
Good luck for the future