Mortgages tend to come in a manor of different forms, from variable to fixed rate and tracker mortgages.
Standard variable mortgages
A standard variable mortgage is exactly that, it varies dependant upon the rate at any given time. Though there maybe repayment charges for early repayments, one thing to watch on any standard variable mortgage is the starting costs compared to previous experience, have a look at the way in which the market can fluctuate to make sure you are comfortable with any likely change.
Fixed rate mortgages
A fixed rate mortgage differs from a variable because as described it sticks to the flat rate you agree at the start of the morgage. A fixed rate mortgage will stick at the same repayment price for the length of the policy, this is great if you want to align your finances and know exactly how much you will be spending every month.
Tracker mortgages
A tracker mortgage will follow the independant Bank of England base rate, this is also known as the repo rate. You will pay at a set amount above the tracker mortgage rate for the life of the policy, the amount will vary dependant upon the base rate, though you will never pay more or less than the tracker mortgage rate. This rate could change dependant upto the bank of england base rate.
Generally mortgages are best suited to your situation, the situation would vary depending upon your requirements and needs, most people tend to stick with the fixed rate mortgage on a long term personal (you live int he house) situation, though you will find a lot of proerty developers will stear clear of the fixed rate.