I passed class 2 in November 2014 and have little if no experience driving these vehicles, probably 10 hours in a wheelie bin lorry (18 tonne) and a week so far on 7.5tonne car transporter. I emailed a company that use hiab class2 and they said if you are interested let us know salary expectations and see if we are both happy. Over to you drivers if you have an idea please.
It’s really down to your personal circumstances. Early on in your career, money shouldn’t be the main motivator. Important to gain as much experience as possible with as many different bits of kit on various types of work.
Clearly you need to pay your bills. Greed never got anyone anywhere. So there’s a balance.
I would suggest you work out what you actually need, add around £5k per annum to it then you’ve got something to negotiate with. Whatever you do, don’t feel you have to work for less than you need.
All the best, Pete 
+1 on peter’s comment. you need what you need! its no good taking a wage that will see you slowly dip into debt, just to gain experience!