You can find out about some forthcoming RHS events from this page
HERE. Not all of the events listed are restricted to ticket entry, many are simply accessed by one's RHS membership to allow free entry, or by the regular ticket entry price to the Gardens for non-RHS members.
It always pays to investigate closely, however, since there may not be tickets available when those are needed, even though no mention is made of that on that page.
For instance, there do not seem to be tickets left for the Colchicum Study Day to be held at Hyde Hall Chelmsford, Essex, CM3 8ET, on 15th September. It may be worth contacting the RHS nonetheless.
There will be various talks etc during the day - including a a photographic exhibition of Colchicum, Crocus and related plants kindly staged by that excellent photographer,Jon Evans.
Colchicum x
byzantinum album - grown and photographed by Jon Evans