John,
Have a look at the ACTC events: there is one in Yorkshire and one in Co. Durham but most are in the South West . Their events are great fun and are old fashioned type trials sometimes involving road work and the sections are sometimes just a steep rocky greasy climb starting in deep mud at the bottom and a restart part way up. Not all of the trials include sidecars, most of the outfits are converted enduros but I have fun entering on my 1950 Norton 500T outfit. Some VMCC sections also organise trials which include outfits: Taverners in Leicestershire, which is well within 3hrs drive of Selby, organise a couple each year. There is a Taverners member active on this site so you may be getting some more info.
Rod