I've just started my new job and obviously they will need to know about my tax etc but I haven't recieved my p45 from my previous job yet so is it as simple as filling out a p46 instead? Do i only have 1 tax code or what? I haven't got a clue about this sort of stuff so any help is appreciated

they recommend you use a p45 but it shouldnt matter although your tax code may be wrong for a bit ie BR tax until they sort it out

When do you envisage getting your P45 from the old employee and when is your next pay day on the new job?

You may have no choice but to go down the P46 route but it will sort itself ...