That winter series is their 'club meeting'
. I'm sure that they must have practice days on Saturdays but i wouldn't know as im not a member of the club. Also a club a bit further down south is usually open on Saturdays from 12midday to about 5pm,
http://www.frankleymodelcarclub.co.uk/FMCC/ . Best bet would be to e-mail the clubs and find out when they're open. Again another track fairly close to you would be Coventry
http://cmcc.sports.officelive.com/default.aspx .