I had free range rabbits for 8 years, always saying that they were safe because we didn't have foxes. The problem is, you never know what day a fox is going to discover you. The day it happened to me was the day I discovered both my beloved babies dead. I also used to say that I'd prefer to see my rabbits happy and free ranging and take that risk, rather than keep them 'cooped up'. I changed my mind after that happened and now think I strike a happy balance between keeping them safe and giving them plenty of space. My lops for instance have a 4ft playhouse with a 12ft run attached; my nethies have a 3 storey 5*2 hutch with an 8ft run attached.
We moved here 2 years ago and recently even here one day there was a load of kerfuffle and there was a fox in the garden at 11am. I'd never seen one anywhere near here before either...
Personally I think it's a huge risk, and that on the whole it's better to provide decent sized secure accommodation all the time. I don't dare let mine out even when I am there, because I know I couldn't catch them quickly enough if a fox did suddenly jump over the fence unexpectedly. Having had it happen twice, in two houses where I'd never seen a fox before, I know that you need to expect the unexpected.
If you do intend to have free range buns, I would suggest investing in an electric fence to go round the edge of your garden.