If it's just a bit of fun and your not intending to get into target shooting seriously then there's no problem in using the Webley to have a go, although it's not a target rifle and the iron sights I'm presuming are not dioptre sights which are more suitable for 10m air rifle. The club may also have an issue with the power depending on the robustness of the pellet catchers! I would therefore ask first.

Does the club have any guns you can use? If so you should try these as they will be more likely to be dedicated recoilless target rifles. The only problem for you might be the weight as adult 10m target rifles will be around 2 lbs heavier than your R10 and scope. The technique you use however is important and with your elbow tucked in it should make the target gun easier to support with practice.