You should keep enough savings so that you could last 6 months without a job. If you are not strong willed enough to not touch the money in a savings account, get a savings product that penalises you for early withdrawl.
there are 3 credit reference agencies: experian, equifax and call credit (in order of size and usage).
all providers of credit ranging from banks to mobile phone companies and car insurers (if you are paying monthly) will report on your account management behaviour.
the banks/credit provider will pay for access to that data which is shared between all subscribing lenders but they dont all use all the agencies.
you can check your data online and many of the agencies will let you do this for up to 30 days for free, after that there is a charge of either £2 per agency by post or whatever they charge online ranging from £6.99 to £14.99.
dont waste your money on finding out your score as all lenders use their own scorecard - its a waste of your cash. there are other similar posts on this very topic which i have answered before so feel free to browse!
Yes - you need to obtain a PUC/PAC? code from your current provider to 'port' your number to the new network. Note - if you are purchasing a new phone check first if this is 'locked' to a neetwork and if so whether it can be unlocked. I've just moved from O2 to T-mobile and successfully 'ported' my number to a new 'locked' mobile.