If you are throwing a corporate event in Yorkshire, then I highly recommend you look to use domes for quickly set up interior spaces. For summertime outdoor events, I recommend you look to have larger, spacious domes. Something in the region of 14-30m should be enough for most events, though larger domes from groups covering corporate festivals typically have larger installation costs.
For smaller-scale events then I recommend something in the region of 6m to 12m in size. This should offer a nice balance of having enough room paired up with keeping things compact to avoid spending too much. If you wish to enjoy an event in the outdoors, you should still have little interior areas for trade shows, speeches, and other events that might keep those who come along involved. So, I think anything from 6-30m should be suitable depending on your choice of event and the attendance level.
