Rental Car Question (Netherlands to Wales)

Yes, it is possible to drive a car with the steering wheel on the wrong side. Foreign registered cars are common in the UK, and millions of Brits take their own cars on holiday to "the continent".
For routes, you have the option of the ferry between Harwich and the Hook of Holland (website: https://www.stenaline.nl/en-GB-nl ) or drive south to Calais and take the Channel Tunnel to Folkestone (website: https://www.eurotunnel.com/ ).
Ferry from Calais to Dover is also possible, but that is slower.

But, I would make sure the car hire company is OK with this. Sometimes they think it is a bigger accident risk (and therefore insurance risk) to drive on the opposite side of the road.

There are certain difficulties driving with the steering wheel on the wrong side. It is difficult to see to overtake. You sometimes have to rely on your passenger to say "go" or "don't go", so make sure your front seat passenger is a driver themselves, and someone whose judgement you trust.
Problem 2 - Paying tolls and car parks. Payment is on the passenger side. A lot more difficult if you don't have a passenger in the car.

If you rent a car in the Netherlands, then the steering wheel will be on the left side. Many Dutch drivers bring their vehicles to the UK so legally that’s permitted. Of course, you’ll need to take more care when overtaking as your line of sight will be obscured. Whether the car hire company will let you take the car across the Channel you’ll need to read their fine print.

It depends what you want to explore in England and Wales as to whether what you suggest is the best option. Alternatively, fly to Manchester and pick up a car there. There’s also a ferry from Rotterdam to Hull which puts you in Northern England.

I personally would never rent a car in a country where driving is on the opposite side of the road from what I'm used to; for that reason, among others, we've never rented a car in the UK. I recall many many years ago renting a motor scooter on an island where driving was on the opposite side. A motor scooter is easier than a car in that regard, yet I remember one time where I made a turn then realized that I had looked in the wrong direction. It could have been a disaster, except that there was no traffic.
We have British friends who had a house in France for 20 years. When they went to their house, sometimes they flew and rented a French car, and sometimes they drove their British car. They had no problem, at least after we met them, but they had many years of experience at it.

Several good points have been made above so I won't repeat them.

I live in the UK and own a car which I drive to Europe several times a year. (your trip in reverse) The first few years I bought lots of extra mirrors (for the rearview mirror, for the side mirror and a wide angle mirror to stick on the side mirror. After a few years (and a few close calls) I didn't need the extra mirrors and took them off. But I did need the eagle eyes of my wife who never thought it appropriate to overtake so I just went for it and dashed back if the way wasn't clear.

Knowing where the centre of the road is remains a fun game.

One thing you will need to be aware of, if your rental company allows the journey, is you will likely have to present the rental car's papers to make the crossing. You will also need to know the number plate of the car to make a reservation, and short notice ferry and Eurotunnel reservations are very expensive - made in advance they are much more reasonable (but still not cheap).

And your rental will have the speedometer in kph. In Britain you need MPH. Important because there are speed cameras everywhere, and some of them are now cunning and measure your average speed. The North Wales police chief has a particular thing about speed limits - and more cameras per mile than anybody else.

It is a requirement that your foreign car be able to adjust the headlights so as to not dazzle or blind oncoming traffic. There are sticky (very sticky and hard to remove the glue) "beambenders" which can be stuck to the headlights. If you use them be aware that they cut down on your vision at night - a lot. Some higher spec newer cars have adjustable angle of attack switches in addition to the weight compensating switch which angles the headlights up and down.

You also need to have the international code for the country the car is registered in on the back of the car (NL for Dutch cars).

Both the beambenders and the international country code stickers need to be removed before turning the car back in. If the glue doesn't come off you risk a damage charge.

First port-of-call though is to ask your rental if you can have permission. If not everything else is of no value.

Landing at Dover (or using the Tunnel on the car transporter shuttles ‘Le Shuttle’) means that you would have to use the M25 to get around London. This is an incredibly busy motorway.

Also consider flying from the Netherlands to England. Manchester airport is well placed for heading into north Wales. Find flights at:>
www.skyscanner.net

KLM also have direct flights from Amsterdam to Cardiff Airport.

While some of the posters here are Brits used to driving into the continent, I would strongly recommend AGAINST doing this. If you've rarely driven on the opposite side, you should not be practicing with the wrong type of car. The driver's side should be on the side of oncoming traffic; it can be very hard to judge your location in your lane from the opposite side. And British roads can be very narrow. Make a mistake, and you could easily crash head on. Why not rent a car once in England?

On some of the backroads - you just drive in the middle - but make sure you can drive backwards to a passing place, should the need arise! https://www.walesonline.co.uk/whats-on/whats-on-news/gallery/most-beautiful-roads-ride-wales-14611567

Thank you everyone for the thoughtful and helpful replies. Flying into Manchester looks like a great option, and that’s what we will do.