it depends on the overall cost, for mortgages where the loan is low the fee works up to be a big cost, hiigh value mortgages the fee has little impact. So calculate the overall cost eg fee + total mortgage interest over lifetime of product
Best to work out the overall cost over product term and compare. Products without fees often have higher rates.
Is it really worth getting new terms with a fee when many deals can be had without?
you can just claim the 20% tax credit , you treat this the same as the mortgage interest (finance cost)
It really makes little difference unless you're raking in 200k rental income on mortgaged properties.