Noddle, Experian and Equifax are all useful in that you can find out about old defaults, bad scoring from late payments, etc...once you know about them you can go about fixing them.
Just don't get caught up with the actual score itself, it's a meaningless number.
IE:
My girlfriend works 40 hours per week, has held a full time job for 5 years, isn't more than £1k in debt and clears just under 20k a year, her "credit score" is 500'ish
My mum is chronically sick and unemployed, on benefits, has had defaults for the last 5/6 years, has just cleared her debts and has a single payment of £50 left, her "credit score" is over 950.