The Milton Keynes Festival of Running is held at the Xscape in the city centre. There is also the option of a 5k or 10k if the half is a little too far! If it's not quite far enough runners can also take part in the 20 miler - perhaps ideal for those training for a Spring marathon.
The race starts on a closed (thankfully) duel carriageway which leads to roads and later cycle paths. It is a relatively flat course although watch out for the challenging hill at around the 12 and a half mile mark. It will slow you down but thankfully it doesn't last too long.