Welcome

Just use brakes. There is no law against it. Braking with your legs may cause problems with your knees. try it out.
Try a flip flop hub, you could then try fixed on one side and freewheel on the other and alternate weekly etc.

Thanks for that. The bike has a flip flop but the fixed sprocket was not fitted and I did not notice that when I picked it up. The shop is sending me a new one so will fit it and give it a go - guess that's really the only way to find out!!