I am going along this Sunday, already entered online. Been doing a few cross-country events recently, so might be a bit of a change doing some road running. Never done a road race so a PB for me even if the course is a bit undulating.
If you do ever get serious hassle like abuse from a large group of cyclists then report them. Generally a large group is either in a race, so report to race organisers/course marshalls with a few race numbers, or a club ride so at least a few will have club colours on. If you have no luck straight away then report the entity responsible to the cycling governing body. Any like minded groups hate it when a few muppets spoil it for others. Cyclists racing on open roads are still required to follow the highway code, I have been in races stuck at traffic lights before, to see a jerk jump them - a shame he didn't getting a finish time as I reported him and he got DQd, revenge is sweet