The gist of BaronG's post is correct but, if you have more than a few thousand hours (I can't remember the exact figure), then you may be exempt the classroom element of the groundschool for the ATPL exams but the study still has to be through an approved school (!)
Also, the highest tax rate in the UK is 40% and has been for some time but you must also factor in National Insurance (another tax!) which varies according to income but reckon on about another 8%.
This might help!
And the actual licence is is at least double the £110 quoted!
Cheers
Whirls