As Trail rat said! Although at the same time don’t over hydrate, easy to do, will make you feel as horrible as dehydration. Water to pour over yourself is a good way of cooling down too. I am going to put an extra water bottle cage on for the weekend, so I can have one bottle for drinking, one for cooling me off. Sleeves will probably be chopped off if it’s hot.
But then I hate the heat! I will probably be the only one praying for rain!
Other advice, eat regularly and mix food types up otherwise you will be sick of sweet stuff.
Either start fast-ish or just accept being a bit held up at the start, you will no doubt have some good, clearly laps later on. Maybe fit fast rolling tyres if it is dry and you have used them before, if not just swap the rear or not at all, better to be confident on the tyres you have. Take some spares with you, being in a team you should be fine to pool your supplies. And take some mild painkillers with you, nothing too strong as your body might have problems digesting them but good to have some on hand just encase…and sun cream! Sounds obvious but at 10 at Kirroughtree last year I was like a one man pharmacy dolling out sun screen!
Enjoy, maybe see you as I go round and round, hopefully, quite scared about it being hot!