If the property ceases to be your owner occupied PPR (Principal Private Residence) then you must stop claiming owner occupier mortgage interest relief. With some exceptions (e.g. being seconded to work abroad rather than simply choosing to go) emigrating would normally mean the loss of PPR status. There may also be other implications in this situation (e.g. need to inform lender, insurance implications, tax issues if you rent the property out etc.). If in doubt you should get professional advice for your specific situation.