I have been to Hitchin several times as Mr B has friends that live there. It is a nice market town. Great for a day out. I think you should tie coming here with a visit to Hitchin Lavender. Both are not a full day out and since it is a bit far from the Lakenheath/Mildenhall area but together can be very nice. There are some chain restaurants and small shops in Hitchin. In fact, I had our cake topper for our wedding made here.
There are several places where you can go to pick lavender and Hitchin Lavender is one of them. It costs £4.50 for a bag and you can go out in the fields and pick it yourself. The time for this is usually June to August. This will give you loads to make homemade soaps and the like. I put them in a little bag and put it in my pillow.