There are a number of considerations. The first would be is it actually dangerous? 

Lights going out when you plug in too much may or may not be dangerous - if folk can then fall down steps they cannot see it is an immediately dangerous matter. Otherwise it is probably just a nuisance, Are there exposed live parts, frayed cotton insulation or things that are burnt and charred by repeated overload? again if so immediate danger. I'd also be very wary of any rubber covered cables as well as this tends to perish over time but it can be OK if the conditions have been cool and free from UV.. Things like no RCDs are not as serious as no main earth, or oversized fuses - its not that long ago since the things were very much optional on a new installation, this sort of not meeting current standards would be improvement recommended, rather than danger.

Then there 'is the is it suitable?' question - now it may be suitable for a weekly meeting and  small dinner gatherings, but by the sounds of it for your sort of event clearly not - the other solution for large events is to treat it like a barn or a festival, and install hire event cabling, either back to the incomer, or if that too is undersized (you do not say what kept blowing) then to a genset in the car park.

And then, as the answer above, the liability and insurance angle - is there a credible mechanism where someone could be hurt (and that really has to be single fault to danger, not some long and improbably sequence of what if events ), and who would be responsible if they did?  Insurance usually drives things like a requirement for periodic inspections EICRs,

If they really are not interested, then there is not a lot you can do after warning them, then they are on their own,.

Mike.

Hi Mike,

Many thanks for your detailed reply (it was the 40Amp BS88 fuse that blew several times). The beer festival has been held at two different venues and both have had power problems / shortages of suitable sockets / documentation. The venue has a number of outlets that are essentially only there to supply the cleaners with somewhere to plug in the vacuum. 

The beer coolers themselves are all RCD protected as is the toilet block.

Should the venue be chosen for next years beer festival more power will be required as  the number of beer coolers was underestimated and there also needs to be environmental cooling (topped out at 28C).

I had assumed possibly wrongly that a building that was had rooms for hire would  a test certificate / documentation etc. I will make these points at the selection meeting in September and will also put forward using a genset to provide reliable power.

Hi Mike,

Many thanks for your detailed reply (it was the 40Amp BS88 fuse that blew several times). The beer festival has been held at two different venues and both have had power problems / shortages of suitable sockets / documentation. The venue has a number of outlets that are essentially only there to supply the cleaners with somewhere to plug in the vacuum. 

The beer coolers themselves are all RCD protected as is the toilet block.

Should the venue be chosen for next years beer festival more power will be required as  the number of beer coolers was underestimated and there also needs to be environmental cooling (topped out at 28C).

I had assumed possibly wrongly that a building that was had rooms for hire would  a test certificate / documentation etc. I will make these points at the selection meeting in September and will also put forward using a genset to provide reliable power.