Multiple vet beds. They are easy to wash and dry and having a spare or two is always useful in cases of accidents overnight: you can just switch them over and wash in the morning.
Slip on shoes or slippers - for quick dashes to the garden. In this weather you'd want something a bit robust and waterproof.
A torch if your garden doesn't have good lighting. So you can see whether or not he has weed or pooed at night.
Plenty of kitchen roll and an enzyme cleaner to clean after indoor accidents.
The Happy Puppy Handbook by Pippa Mattinson which is awesome.
A small variety of toys so he can investigate them all and start to discover what he likes to play with.
A soft brush so you can practise grooming early to get him used to it.
Some rice to keep in store in case of upset tummies.
Baby gates to shut off access to stairs and front door (if your house needs them).
Plenty of healthy training treats dotted around the house so you always have one to hand to recognise good behaviour.
Recommendations for a good vet - and an appointment within the first couple of days of getting the pup, for a check up.
A lightweight collar with a good range of expandability because puppies grow quickly. A little dog tag.
Some nice bubble bath for when it's been a long day filled with doggy muck and all you want is to relax and feel clean and human again 