Whereabouts in Sussex are you? There are clubs across the county that do regular trail running so I'd agree with JR's advice, contact a local club and go along for an evening. I don't currently belong to a club myself, but most are pretty friendly.
Re training plans, I also agree with JR, except that I'd add in additional hill intervals if I really wanted to push my time. Also, if you can't get out for three days of the week, there are some excellent exercise programmes for trail runners, that involve about 30 minutes a session and can be done at home. Have a look round Youtube or similar. (Sorry, I have lost my links to the programmes I used, as they were on an old computer )
Well done JR. A PB and a win are very nice to get.
Assuming the challenge is still going, I hope to be back next month. Had some problems since tearing the calf, but things seem much better the last few weeks. Completed a slow steady 13.4 this morning as a training run.
I may not be part of next month's challenge, as I've managed to injure my calf and hurt my back. Nothing too serious, but it'll probably be two weeks off running. But, in the words of one of my favourite fictional characters ... "I'll be back!"