If you have a phone contract with limited tethering data, there is an app you can get called pdanet+ / foxfi, which does something clever so you can tether as much data as you wish without it coming off your allowance. The free version switches off at random intervals, but the full version only costs about a fiver and let’s you leave the tethering on indefinitely.
Sorry, thought I’d posted this in the techy forum…
seems to have a lot of negative reviews.
I’ve been using it for the last 6 months or so, and had no problems at all with it - its a ten from me 