Owenski

Been in a similar situation myself hindle.
Just a note it may have been covered but have you considered that your current company are actually paying you for what you are giving them. I dont mean that your a slacker or anything lol I mean because you loose 6 weeks through training.
eg if your doing a job that other people are getting £24,000 a year to be doing but your only earning £22,000 for the same job. But your doing the training course for 6weeks a year then your actually getting paid for the time your spending in work. Your hourly rate will work out the same as the rate of people doing the same thing for 24grand a year but dont go to collage.
I had a similar discussion at review time with my employer, how come people who I can do more than and work harder than are earning more money than I am. Simple answer: 36 days out of the year that Im not here, they are.

It would explain why these other companies would offer you the position on a the higher salery but then refused once you requested about working for that money but missing 6weeks of work. 6 weeks is a long time when you look at it anually.
The good news is that once you complete the training then they'll have no excuse and many other places will be more than happy to take you on the higher wage packet.

EDIT: If someone can understand what it is I've written here can they re-write it so it makes sense to everyone. I cant think of how to word it better but it may be quite helpful to Hindle if he hasnt already considered it himself.