Thanks Ray, I think we need to get in to some of the vans we like the layout of but I am not overly keen on long travel with covid on the go.
There really is no substitute for visiting actual caravans, layout in catalogues may show you where things are, but they don't show you things like the edge of the table that always gets you when you need to slide into the seat for a meal, or the overhead locker that tries to knock you out when you sit up in the morning,
I am pleased you're taking C19 seriously, unfortunately I fear that some people still don't, and they are putting vulnerable people at risk. So I suggest to you that perhaps delaying your real searches until you are satisfied the risk is justified.
Because you have Cat BE on your licence, and a very capable tow vehicle, the car is not going to limit the size of or weight of caravan you could use. This means your major priority is going to be layout.
Take your time to consider the pro' and cons of different layouts. By all means consider what others opinions and points are about what works, that may be useful to you, but it's what 'll work for you that counts. When you feel it is safe to do so, go and look at some.
I agree with lady Mel that condition is more important than age. However inevitably as caravans age they do tend to deteriorate sometimes just through ageing, and of course they may have been used more. An incomplete service history might suggest a previous owner has not looked after the caravan.
Otherclive has made a very valid point about the materials used in the construction of caravans. I would suggest you look for newer one (less than 10 years old) with a low wood content in the wall construction. It doesn't mean they won't leak, but the ensuing damage may be easier to repair if it happens.
Sadly for a novice caravanner (and even some well experienced ones as well) there are some pitfalls to buying a caravan, and especially secondhand ones. create a list of specific questions you want to ask about the caravan. Make the open questions so the responses have to be full and informative. if any of the answers are unclear or unsatisfactory you should be suspicious.
So don't agree to purchase a caravan without having the caravan professionally and independently inspected. If the seller refuses to allow you to do this - walk away. If the inspection turns up something that seems iffy about Its condition, and you cant resolve the detail - walk away.
An inspection is generally money well spent as it can point out issues that you simply aren't experienced enough to know about. It might give some leverage to negotiate a keener price.
When paying for the caravan, pay a deposit of at least £100 using a credit card (not debit) as this will mean you get some additional protection through the Consumer Credit Act. Also you might find reading up about the Consumer Rights Act 2015 which also spells out what you should expect a seller to be responsible for.
Don't rush.