Borrowing on Mortgage - Guidance Appreciated

SparklyRed

Hello. Thank you for reading. I will, of course, arrange an appointment with Nationswide, but until then, wanted to share some information and get some advice if possible. 

I bought my house 5 years ago and have a 5 year fixed rate mortgage at 2.54%. Nationwide have offered me the option to do another 5 or 10 year fix at 2.54%. For context, I have £128,000 outstanding and the house is worth £250,000.

Question 1: If I fix making no changes, would I be best going for 5 or 10 years? I am about to switch careers and have a new job secured and ready to start. I will earn about £1700 per month and my husband earns around £2000 per month. My salary and my husbands will be relatively stable and aside from unforseen circumstances, I cannot see much changing. I have a 3 year old, no plans for more children and am not anywhere near retirement age. 

Now to the more confusing part. I have a personal loan with £13,500 outstanding and between us, my husband and I have around £10,000 on (currently) interest free credits cards. He is not on the mortgage. Between these debts, we pay just under £700 p/m for the mortgage and we pay a further £600ish covering loan/card payments. With household costs, childcare and other things in addition to mortgage and payments, we don't have much left over and I am always in my overdraft beore pay day. We have had a major renovation project on our home but the builder was not good and so we've incurred additional costs and still have things to pay for to fix/do but we have nothing left financially to do so as we haven't been in a situation where we can save up. 

One option we have discussed is adding my husband to the mortgage and asking to borrow £25,000 in addition to renewing the mortage deal, so that we can pay off all the debts, use the monthly excess to complete the house and once donwe, use the excess to overpay on the mortage. I'm asware this incurs costs with having the debt for longer, but in the short-term, it does give us financial flexibility that we simply don't have now.  

Question 2: Are we being really stupid considering this option? Has anyone done this? What would be the financial implications? Would monthly overpaying reduce the amount we pay back in total?  

Any advice or information really gratefully recieved until we can see the mortgage advisor! Thank you.