Hi Crouton - hope you have a great time in Oxford, I got married there so have happy memories. Nice place but parking is impossible in town, so go for the park and ride.
Anyway, UK coupon use. We do use them, and as I have posted elsewhere (but it got deleted as I think the mods thought I was inciting people to illegal coupon use in the US, LOL), MOCs in the UK can often be used for items you haven't bought, and it's not illegal here. Some, but not all, Tescos and Asdas will let you use, say, 50p off soap when you haven't bought any toiletries at all, but we don't have the high volume of coupons that you have in US. No inserts in the papers I'm afraid. There are often single coupons in newspapers and magazines, if you want to find what is available go to
Money Saving Expert: Consumer Revenge - Credit Cards, Shopping, Bank Charges, Cheap Flights and more, a very useful UK site, and type 'newspaper coupons' in the search box, that will bring up a daily thread that gives all the available coupons. You can also find coupons being given away on promotional stands in supermarkets, shopping malls, etc, you just have to look out for them.
You will find a lot of BOGOF offers, and stuff reduced in certain areas of the supermarket, usually at the end of the day. Also, if you shop at Tesco make sure you get a Clubcard and collect points on it which you can exchange for money off or for deals.
The best way to keep food costs down is to cook from scratch as much as possible and avoid ready meals and takeaways (though you must have some fish and chips while you are here, and of course a good curry!). Most supermarkets have a Value range, which are often as good as brand names but not always, so worth experimenting.