If you’ve just locked yourself into a 5 year fixed that you’re struggling to pay, a 6 month interest only situation is only kicking the can further down the road. What happens in the following 4.5 year period?
You’ll have to speak to your lender to find out what approach they would take. Its either increase the term of the whole mortgage, or increase your repayment amounts over the life of your existing mortgage deal.
You’re probably going to have to jump through a lot of hoops to get the lender to agree to pausing things, especially if you’ve only recently agreed to a fixed rate deal. Cross your fingers and read the small print.