Seats in the back of 109/110 hard top

Since my last thread about getting an 88 Series for local bimbling & occasional use I've been doing a bit more thinking. We live in a nice bit of the country and it'd be good to get out with bikes, kids, kayaks etc. An 88 or 90 is going to be challenged on capacity. A 109/110 wagon (relatively few 109s around it seems) would fit the bill better but I think its load area will still be a bit short especially for bikes.

A 109/110 hard top/panel van seems like it could be the ticket. With a couple of sideways-facing seats in the back, either the usual benches or the fancy Exmoor high back seats if feeling rich. Clearly not great for long trips but that's not how it'd be used. We have a people carrier for that.

Anyone have experience of this layout? And, perhaps more importantly, anyone have experience of changing the V5 to add seats in the back? Used hard tops seem about 50/50 on whether they already have back seats. Just wondering if it's worth me considering any that don't already have seats; I probably wouldn't bother if updating the V5 is really hard/impossible.

Adding seats is easy enough- just bolt them in. If you want seat belts, 2-point lap belts only, bolted through a substantial steel plate on the underside of the seatbox. The seat belt is more to stop passengers sliding around than any real safety benefit. Disco 1 rear seats are flatter when folded than Defender seats and so don't take up as much load space. If you want windows these can be installed too.

The difficulty tends to be in changing the tax class if you wanted it to be classed as a car rather than a van. This is relevant to things like the London LEZ, and there are a few converted 90s around which were formerly a hard top but are still classed as such.

I've never had to think about whether something should be taxed as a van or as a car before. Those decisions have always been made for me! From what I can tell it could be taxed as either and I could still use it for private purposes though, right? Adding two seats doesn't seem like it would automatically change the tax class. Though most of the info I can find is for vehicles that are... quite a bit newer than the 109s/110s I'm looking at

We're in Northumberland so I don't think taking it into an LEZ is going to be an issue. Especially not if I end up with a 109 Series! So I don't personally mind whether it's classed as a van or a car; I'd just like to avoid as much paperwork and tax hassle as possible.