Blimey, you are going to be lucky to match that lot.
The good news, you are closer to Wales / Surrey Hills / Swinely. The bad news, South Downs is about it…..
Try looking at Rogate, in Petersfield (DH), Tilgate Forest (Crawley), QE Park in Pompey (XC), Lordswood in Southampton (XC, little bit of DH), UK Bike Park, Shillingstone (DH).
I shouldn’t knock the downs, great rolling singletrack in the summer and slippery muddy slog fest in the winter. It’s got it’s good bits, so worth digging out an OS map and exploring the Bridleways.