Hi Funny Hat,
I'm also from the Reading area, and a few races I've either done or heard about are:
May
Woodley 10K, very local/easy to get to, fairly fast road course.
Shiplake 10k, also fairly near, off road with some hills. nice scenery, and has a school sports day feel, so family friendly
(Also in that time scale, there's the maidenhead 10 miler, always on good Friday, I believe, not the most scenic course, but a different distance to normal.
august/early sept
The Maidenhead half was in early sept this year, was their first one, and once the few teething problems are sorted, it's a nice course and quite fast.
october
Reading O2O 10k, not done this myself, but is supposed to be quite good, and it's in Reading so no transport issues.
Halloween 5k night run, shorter distance than you specified, but I've heard it's quite good fun, running with just head torches. Not done this myself, as will be in Dublin doing the marathon, also recommended, as love the course and the city.
end nov/december
Rugged Radnage 10k, did this last year for their first one, tough, muddy, hills, but good fun.
grim challenge original, very different to normal, running through puddles and under cargo nets. on the expensive side, and more fun as part of a team than a solo runner.
Just a few more ideas into the mix!
Martin