ZWILLING Henckels International Self Sharpening Definition knife block 7pc, Metallic £64.99 (Prime Exclusive) @ Amazon

Long history, British brand, good looking. Not sure if they still make them in The UK. I think Viner Titan are more than decent. But I think they are in a different league. For home cooking, yours are probably more than fine and certainly better than the average brands in the shops. However, reading online, I've not come across any chef talking about them. I just read an article about Gordon Ramsey, and Henckels was mentioned as one of his favourite brands. I really much doubt it he believes this. There are better brands out there. He probably said he likes Zwilling, and his words were twisted and associated with Zwilling sister company. Or he uses the 'highest specs' Henckels model.
We don't have to believe what the famous chefs are telling us. It is all marketing.
I think your knives are good, but probably in a lower league than these ones. Personally, if there is nothing wrong with them, I would stick to them. And if I were to replace them, I would have gone with some top brands. 3 x Zwilling Pro knives are £100 and I don't think you need more than 3 knives. Quality over quantity.
Saying this, the price is very good for these knives. (edited)

Sheffield steel made in a basement in China and with a tag stating made in The UK

Not really. That's more for keeping them sharp, rather than sharpening. For sharpening, you need to move the knife in and out quite a few times. I've not noticed any residue when taking the knife out.

Well, the ones you've got are great. And more than likely, you don't need extra knives. Yours are better than Zwilling basic pack of 6 plus knife block listed here at £150. (edited)

The ones with 2 fellas are the more expensive ones, made in Germany or Japan. I've got them, and while the knife block has 2 fellas, it is made in China. But the knives are made in Germany. The ones I have are Zwilling, not Henckels. However, they are still stamped. Zwilling budget models are stamped as well. I've paid £110 for Zwilling when Henckels were £70. I thought the £40 difference was quite high, as Henckels are good too. Now, Henckels are £65 and the Zwilling I've got are over £150. I strongly believe the Henckels are way better value now and are good knives. I certainly prefer Henckels rather than the recent deals on Ninja knives at £130. Not only because they are cheaper, but I feel they are better quality as well. (edited)

I've paid £110 for Zwilling when this one was £70. I was tempted so many times to cancel and to go for Henckels. Eventually, I decided I like to see Made in Germany printed on my knives.
However, given the fact Henckels is £65 now (up until midnight) and Zwilling is over £150, no doubt in my mind, if I was to buy now, I would've gone for Henckels. If you can spend a bit more now, put an order on Henckels too, and once received, see which one you like more, and return the other one. (edited)