You don't want to spend hours on the road in October when light is precious so ai for courses which are close together.
If you want a third course to go with Woodhall Spa and Seacroft (both well worth playing) then I would suggest you consider Lincoln GC at Torksey 12 miles north of the city (which is also a must see)
www.lincolngc.co.uk You might also consider Blankney, which is south-east of lincoln and therefore closer to Woodhall Spa. For that matter, why not give the Bracken Course at Woodhall a whirl and let us know what it is like.
As a third course to go with Notts and Sherwood Forest I'd suggest Coxmoor
www.coxmoor.freeuk.comI share Sean and Tom's enthusiasm for Beau Desert. I also agree that it is good to play Whittington Heath before BD. Using the M42, it's not a major journey from these to Notts.
Somebody mentioned Frilford. Take care! It all depends on which course is in play for your number of players. The Red is the course to play, but they alternate 2- and 4-ball play between it and the shorter Green Course daily. The Green Course is not bad, but I don't think it is worth the journey in its own right. I don't much care for the new course there. Also Frilford is some way distant from beau Desert and out of the reckoning for Notts. However, if you fancy a couple of nights in the Cotswolds (which can be gorgeousin autumn) you could combine Frilford with Huntercombe (vintage Park) and Broadway (great views, excellent drainage, some really fun holes) and/or Tadmarton Heath, a great little heathland course outside Banbury which seems not yet to have caught the attention of GCAers. None of these is far from Woburn, either, which is always a delight.