I have had 5yr fixed mortgage and wish to change mortgage company

Assuming your fixed rate period has now ended it should be a simple question of choosing which company you would like your new mortgage with, checking you fit their criteria, and applying. What exactly is it you need to know?

You'll probably find rates are lower now than they were. I'd suggest a chat with an independent mortgage adviser who will be able to suggest a solution tailored to your needs after s/he has completed a full factfind of your situation

it can be bewildering to compare all the deals available, can't it?? You could look at the mortgages listed on this site, but I really would stand by my advice to see an independent adviser

An independent advisor can look at lots of different mortgage providers to find you the best deal available at the moment - but make sure you are outside your fixed rate period as if you are still in it you could pay a penalty to move. Have you asked your current mortgage company what they an offer you as sometimes you can switch to another product at reduced or even free rates.