Yes you do the venue you are using should also have it also whoever pays your club insurance should be able to tell you if your club has it and where it can be located .
Also it is a legal requirement to have the certificate on displayat the your club
Finally, a topic I feel vaguely confident commenting on!
I underwrite liability insurance for a living, the venue will have the coverage, however it seems strange to me that they would ask for your cover. Unless they can prove you were acting negligently in the use of the nets (via CCTV) then they would struggle to bring a claim against your club.
Also, just as a point, you don't have to have a Public Liability certificate displayed in your clubhouse, most companies wont even issue a certificate for this cover. As technically, it's not a legal requirement in the same way that Employers Liability is, for instance.