I can’t understand the mentality that prioritises keeping bikes in the van and doing the cooking outside the van.

Keeping bikes inside is number 1 priority for me. Having a couple of expensive bikes on show for all to see is not conducive to a good night sleep.

That.
There’s the usual problems of external racks, parking prangs, road debris being kicked up, that sort of thing, plus the security issue. A weekend away may involve staying at a friend’s, bikes inside the van no problem, get back late and knackered, bikes inside just leave them. Height/length less of a problem on ferries, shorter so easier to park, inside is far, far better.
Cooking outside is often very pleasant in the summer, which is usually when I’m staying in the van. Can still eat inside if it’s raining.

Covid put a delay on this – but still planning on getting something sorted by next summer.

How essential is heating? A diesel heater adds a deal of complexity and cost to a build. If a van is well insulated and keeps the bulkhead, will I regret not having heating?

Main use is going to be summer, but Autumn trips to north Wales also need to be factored in.

We had it fitted in our T4. Never used it! During the colder months we tended to stay on sites with hook up anyway so used a small fan heater or tiny oil filled radiator.

Not needed in summer in my opinion. Lots of people say it’s a must. We are not putting it in the T6 we are getting converted and will see if we miss it (can always add it later).

If it was just for you, I’d suggest the Puggy Partner – depending on length of bike you could get normal length or the slightly longer one. With a single airbed on one side and bike on other you could easily sleep and travel in one. Washing/cooking would need to be done outside but why stink the inside out more than it needs?

That would be properly basic but mean the basic need.

Saw a conversion on YouTube (unfinished) with the standard 3/4 rock and roll with side kitchen and storage in a LWB to provide some boot space.

The twist was that instead of a permanent bulkhead and bikes going in the 18-24″ space at the back, the bulkhead was fixed to the seat. The seat would slide all the way up to the front and had brackets on it, so for day trips you could put a couple of bikes in there without any dismantling. If you were staying away, you take a wheel or two off and it fits in the back against the bulkhead.

I had an Eberspacher in my lwb Transhit which was great- however two downsides:

1. You need to drill quite a few holes through the floor for air inlet, exhaust and fuel supply.

2. They are noisey buggers, the fuel pump clicks and the inlet and exhaust both need silencers fitting to not annoy fellow campers/yourself!

I’ve got a propex, much quieter than the Eber on my work van.

Rarely use our heater. Occasionally in the morning in the colder months, and even then only when the GF is with me.

Decent sleeping bag /duvet at night, a down jacket and a cup of tea when you’re up.