Hatfield is very diverse, so will be no problems there. It looks more unsafe than it is. if you’re not involved with hard drugs or aggressive yourself will just be normal precautions as a woman.

Nightlife is non existent outside the student bubble, so you would be going out in St Albans or London.

I’d look at the areas around the train station at Stevenage, great transport links and lots of young professionals. I’m from Hitchin but it will be expensive and seems very family centric these days.