I know of a couple who were in a similar situation. They applied for a loan with their Irish bank before leaving, citing the reason as personal expenses. They did not inform the bank that they would be emigrating. It was approved based on their credit rating and current income in Ireland. They then moved abroad and paid the loan back from their Irish bank account by direct debit. As far as I know, the bank was none the wiser.
As an aside, getting credit in the UK takes time and effort. Even if you don't plan on needing credit there, you should start building your credit history right away, just in case.
There are several high-APR credit cards with low limits, which you can use for bills/groceries and pay off immediately with your debit card. After a few months, you will have begun to build your credit rating. You can also apply for a bill-pay phone which will further boost your rating.
Best of luck with the move.