Stating the obvious maybe and far easier to say than to do but you will do far more for yourself than improve your credit score if you do this.

Credit cards certainly have their uses but can easily be overused. You should ensure that you are paying as little as you can for their use by keeping their balances down, ensuring you make the correct repayments and by sensibly shifting balances to cards which carry less interest (while not maxing out any particular card). Additionally you should pay off debts before you save money as a general rule.

Discount mortgages are a subsection within variable rate mortgages with the discount being applied to the lender's standard variable rate (SVR), which is itself linked to the Bank of England's base rate, although the lender can chose to alter its SVR autonomously.

You benefit from the discount although you are taking a risk that the rate won't suddenly increase, leaving you with increased repayments regardless of your discount. You should also be aware that the discount normally operates for a fixed period of time. Once this period has elapsed, you are placed onto the lender's SVR although you can change mortgages and/or mortgage providers at any point. During the time of the fix, however, there are likely to be large repayment charges levied if you opt to leave early.