The mod you have is eleaf, the Nautilus tank is aspire. Not that it matters any 510 tank will work on your mod. But it seems you are conflating products and brands.

The nautilus tank and the coils for it should be available at many places in the UK and online for a long time (the authentic ones SKU 1859402, not necessarily the clones you linked to - I'm surprised they don't taste like a used diaper but then at 7W I guess there not much flavor to be had - good or bad).

Aspire did make some new versions of the Nautilus tank in the past couple of years, but they still take the same coils as the original nautilus and nautilus mini. FT doesn't sell those newer tanks or much Aspire stuff because aspire hates FT as they have sold a lot of cloned aspire products over the years. Aspire gets butthurt as easily as you and I sneeze in a dust storm. Same with Smok.

Anyhow, the point is, for your vaping wattage just stick with what you have and like. I can understand wanting something mote modern when you can't get the stuff you have anymore, but that isn't the case with what you have.

The Nautilus achieves true MTL so keep that in mind if a proper MTL vape is what you require. Most tanks that pretend to be MTL since 2015 are loose MTL if they can be classified as MTL at all.

However if you absolutely want change your tank, then I strongly suggest you look into the Innokin Zlide SKU 9712526, Zenith SKU 9674054 or Zenith II SKU 9742482 tanks (but not Zenith Pro). These are very popular MTL clearomizers today, kinda stealing the title from Aspire. They take the Z-coil and you aren't likely to find clones of them. But many MTL vapers love the tanks and the coils, especially the 1.6 ohm SKU 9674059 and 0.8 ohm SKU 9674058. Lots of troubles with the 1.2 ohm. I'm not sure how either of these coils will perform at 7 watts though, so that's why I say stick with what works for you since they are easy to find and will continue to be easy to find.

GOod luck.