Mortgage Term

Hi,

I have a quick question that I'm sure can be answered quickly!

I'm looking to port my current Interest Only (IO) mortgage (25 year term) to HSBC 5 year fixed rate mortgage. I would like the mortgage to remain IO but HSBC have said that as I just hit the 75% LTV rate they can only offer me the IO mortgage over a 15 year term. If, after the 5 years are up, I look to port the mortgage to another provider will there be any issues with me increasing the term of the mortgage to say 20 years?

In short my question is - will I experience difficulties if I accept the 15 year mortgage term from HSBC and wish to port to another provider and increase the mortgage term in the future?

I hope this makes sense!

Thanks in advance,
Andrew