UK LADIES

Hi all, I'm going over to Scotland to meet my in laws next week, I'm from Australia so I'm not too sure how I will cope with such cold whether. I really need help with the type of pants I could wear - sounds silly but cause I'm bigger now I can't wear jeans cause they hurt my bump. Are their any GOOD stores for maternity wear over there?? I can wear leggings here on a cold day and be fine but my fiancé says I will freeze with them and the "UK wind" lol help me!!!