There are races of all distances all winter. Those of interest [in my opinon] in the Kent & the south east are :
5M; Portsmouth, The Christmas Cracker [my race on boxing day].
10K's; Southend, Brigton, Hastings, Ashford, Hyde Park
10M; Canterbury, Woking, Thanet
1/2; Camberley, Paddock Wood, Tunbridge Wells,
Other little gems like A Christmas Caper 4.2miles at Swanley [free xmas pud]
Of course there is plenty of XC. I race in the Kent men's league, county champs, & national & southern champs.
The Running Fitness league caters for the friendlier club members & is less high profile.
You do get some open xc races but not many.
No Rest For The Wicked ;0)
Tim