One of the advantages of a marquee wedding is being able to choose your own outside wedding caterer. Wedding catering can be a large cost at a wedding venue and you won't have much choice in which caterers you can use, however if you have a marquee wedding, the marquee catering options are endless.
They will set up a mobile kitchen on trestle tables in a catering tent - usually the end of the wedding marquee which has been partitioned off, and will usually also have a refrigerated van. Alternatively, go for a country theme with a wedding barbecue or hog roast, or provide your guests with picnic hampers and rugs.
Don't scrimp on mobile loos! For around £200 you can have a pair of tardis toilets - those awful ones you find at festivals and on building sites, or for £450-£550 you can have a proper trailer with separate ladies and gents flushing toilets with proper basins, towels, mirrors and even a vase of flowers. It is an easy choice and your guests will appreciate the extra space to touch up their make-up. There is a growing industry of wedding luxury mobile loos, so it is likely that there is a supplier near you, and you may find that your marquee company can recommend one they regularly work with.