Geodesic tents are the usually expensive, do exceptionally well in severe weather tents used for high level mountaineering and are probably overkill for a larp at less than 150m altitude. Although I would be deeply suspicious of any geodesic tent being sold for £10.
Tent choice is always a compromise on weight vs space inside vs surviving adverse weather vs affordability. Of that set you can usually have a maximum of three.
I’ve used a small 2 person dome tent similar to (https://www.millets.co.uk/tents-camping/107840-eurohike-tamar-2-man-tent-green.html/) for all of empire including the year when I was travelling down by public transport from northern Scotland it hasn’t failed in the wind (yet) but I’ve watched lots of larger tunnel tents with a bigger cross sectional area catch the wind and end up completely destroyed.
Jasperleigh - How are you travelling?
If you’re coming by train to Banbury and then the minibus to site there is a shopping center with a M&S fairly near the train station and if you’ve got a gap between train arrival and mini bus pick up it’s quite easy to walk over and grab food.
There is a Tesco at Towchester which is probably the closest to site by car which some people do trips to on Friday Morning so if you can find someone going you might be able to get a lift.
Some people do online food orders that they get delivered to the entrance of site, although you then need to be at the entrance which is quite a distance from the playing field when the order arrives.
There are also caterers who sell food on site. It’s generally about £6-7 for a hot meal.
Tent wise, I would recommend either finding someone else attending site with space in their tent and asking to share or buying a tent ahead of time and bringing it with you. Nothing is worse than trying to put up a tent for the first time in the pouring rain and finding that it’s missing a piece or doesn’t work out how you expect.