Groceries
You could bake a casserole, grill a steak or make a full English breakfast in a narrowboat galley. It might be difficult to bake a cake with only a whisk for mixing, but it can be done.
I suspect, however, that most people only get enough groceries for breakfast and lunch, because you’ll want to eat at pubs along the way. On our trips, however, there were one or two nights when we were moored miles from the nearest hot meal.
It might seem anal, but create a shopping list of what you’ll need before you pick up the boat. Agree on common items like sugar, bread, milk and butter (and agree on what you mean by those generic terms) and then agree on individual items so that you don’t end up with a mysterious can of ox-tail soup no one can remember buying.
Fortunately there’s almost always a grocery store either close to your boat hire or at a wharf along the canal. Long time boaters understandably might grumble at Tesco or Sainsbury’s replacing an historic building, but you’ll be glad of the convenience. Use Google maps or similar service to find the grocery stores along the canal.
Bed and bath
There may be a first-aid kit on board but don’t count on it. You may want to stock up on cold remedies.
I recommend bringing your favorite cold medicines from home. Trying to divine the UK equivalent of Nyquil can be maddening.
Duvets and bottom sheets are provided for all the beds along with towels for all the listed passengers, but you probably won’t have washcloths/facecloths. They’re considered too personal an item and most UK travelers bring their own.
A narrowboat bathroom is understandably tiny and the toilet is usually perched uncomfortably high because of the sewage tank underneath. The flush lever is located at the base of the toilet. You pull up to let water into the bowl and push down to flush. There’s usually a tiny sink and a tiny shower (one boat we booked had a tiny tub). There’s a separate pump switch that drains the shower or tub. Gray water is dumped into the canal.
Don’t expect the soaps and little bottles of shampoo and hand lotion that a hotel would provide. You can’t use the hair dryer you brought, but instead have to be content with the provided anemic 12V device.
If you’ve not traveled outside the US, you may be unfamiliar with duvets, which replace the top or flat sheet most Americans use. The duvet has a removable cover that is washable. The duvet is not tucked under the bed. It’s essentially a comforter. They are evil.
You’ll probably have to get toilet paper at the first opportunity and paper towels to supplement the one provided hand towel.