Its not a permanent install, i will pack up after every gig.
AND the system will be used in other halls in London.
In that case sure go for it, would maybe look at getting something that you can use to scan RF with though, if your event is at all high profile a wireless dropping out is a big issue. Likewise maybe some directional antennae are not the worst idea, I can imagine London is quite active and some null points on your antennae might actually be useful.
I've also never had issues with big bags of water(humans) blocking RF with a handheld mic and since most belt packs tend to be placed behind people I find the rear positioning to be better but YMMV. Did have dropout on one mic that followed whatever frequency I selected, I happened to be rewiring the rack and reseating the BNC connectors solved it immediately... Should generally be step 1 for troubleshooting the more I work in this industry the more the problem is quite stupid, like a connector being partially disconnected or just not connecting correctly due to corrosion/oxidation.
Maybe the issue is that your guys have the mics down by their stomaches the whole time and not near their head where it should be.
Also I would strongly recommend power conditioning/UPS for the wireless mics, power issues cause massive headaches with wireless.
Regarding different cable lengths I would likely hope that Henry can pop by and give is some actual science on that.
