I checked earlier and found out the April 5th radio hanger sale has been cancelled due to coronavirus along with a Militaria fair in May.
Hopefully they will rearrange them for later in the year.
https://hackgreen.co.uk/whats-on/hangar-sales/
Also have a look at the pdf statement or check the website if you were thinking of visiting the bunker, as they have changed the opening hours/days too.
David