It is often the case that either the County Council or the Highways Agency will own the land along the roadside. Likewise, the strip along the railway line is usually owned by some offshoot from the old British Rail.
How about parking somewhere that you could then use Seagull Travel or NWSussex seagulls coaches? Coaches get away fairly quickly after games so depending on your route, maybe a pickup just off the A23 or A27 would work for you.