This assumes you have no 2 crew time.
1. Do the CAA medical at Gatwick. GBP 235
2. Do an approved theory groundschool, best bet is distance learning. 2000 pounds or so.
3. Sit all 14 JAR ATPL exams. ~GBP750
4. Min hours req'd to convert the IR, 15 hours.
Budget at least GBP 6000
5. CAA IR exam fee GBP 575
6. Go to Gatwick and get the lic. ~GBP 100
You'd need to factor in cost of living and other such expenses.
To verify go to
CAA
To be honest, without any turbine time or multi crew you would just be joining the ranks of the locals that are trying hard to get a job. I don't know your hours but any thing less than 1500 hours piston is considered "low hour" here. (At the moment)