Hi mate your rod will be fine. The important thing on your first time at a casting day is to take it as it comes and enjoy yourself, get your first measured cast then try to beat it. I wouldn't worry about the members fees for NESA either, you can go along as a day caster (it costs a couple of quid more I think) then if you are going to go most months join up.
Key things for your first time are plenty of spare line (Sakuma Nite Crystal in .31mm is best for the 150g), high viz shockleader of 80lb and being up for a laugh and to learn. If you get the bug then great, see where it takes you. Don't worry about your rod it is more than capable of 200 yards over grass the only concern might be that at 15' it may be difficult to handle with a powerful style.