I found wild camping fairly easy in England, on my recent JOGLE I wild camped every night. You will find a spot, some times you have to ride a little longer than you might want but after a long day riding you seem settle for any where.
One night in Cornwall after a big ride I spied a turn off, I pulled off the road and up the forestry track....it kept climbing with nowhere flat enough to pitch.....up and up I pushed my heavily loaded big dummy..eventually I I found a very tight pitch near the top of the ridge and popped the tent up just before the rain hit. Popped the cork on a bottle of Shiraz and watched the sunset while scoffing noodles...bliss.i also camped on Dartmoor in a big storm which was great fun. One thing which makes life easier is some EU thing, farmers are paid to leave an uncultivated strip about 5 mtr on the edge of many fields, great for wildlife and just big enough for tent
England is I busy place but once you get out of the big cities there is always a small wood or field, if your solo and don't leave any trace then no worries. If you leave yourself with wild camping as the only option you WILL find somewhere.
Personally I couldn't tie myself to a booked campsite and either have to slog it or pull-up short. Ride enough, camp, repeat.
Although technically illegal in England your not going to be arrested or harassed unless you pitch up with with caravans,dogs and a rave tent etc.
If you're uncomfortable with the idea of it make yourself do it! Load up the bike and just pedal, don't take a credit card or money, when you get to the point of no return......find a field.