No MM stage, so I’d still need to purchase one. This will be my first turntable in about 15 years, so starting from scratch.
The simple way to look at it is that MC is harder and more expensive to get right.
The cartridges are more expensive. Yes, you can get MC carts that cost less than some MM ones but they don't sound massively better, they are just different. If they were massively better everyone would be buying them. You need to spend a lot on a MC cart to get something special. But at the lower to mid range MM carts absolutely dominate.
The other reason for that is that MC carts are harder to get working right. You need a very good turntable and arm to get the best out of them. Yes, a MC cart will work on pretty much any Rega tonearm but if you invest the money in a better arm and cheaper MM cart you'll get better sound.
MM is also less aggravation. Manufacturers seem to have a hard time making a bad MM phono stage, I have one here that cost about £15 off eBay and it sounds fine, but making a good MC stage is trickier. You need to spend more before they'll really let you hear what MC is about. You can't replace the stylus on a MC, you need to replace the whole cartridge, and the much higher gain means you're far more likely to get issues with hum and noise. Overall, unless the rest of the kit is at a pretty high level already MC just doesn't make sense.
The other thing is that this cartridge is used. Unless you know the history, and not just what the seller is telling you, you more or less need to assume that a used cartridge is scrap. It'll certainly be worn and you don't know how much. So you buy a MC phono stage and hook it all up but it doesn't sound great and you don't know why? Is it supposed to sound harsh and edgy? Is the phono stage not very good? The only way you can eliminate the cartridge as a possible cause is to replace and the current version of that cart is £300.
If you want to go for it's up to you. Personally, I'd sell the cart and buy a decent MM. I'm sitting here just now with a Rega Exact on an RB3000 because...I prefer the way it sounds. And I've had a bunch of decent MC carts, I have an OC9-XSL here right now which is one of the best MC carts I've had, and not the most expensive. And I have a Rega Aria phono stage, which is not shite! But the Exact connects me with the music more. Yes, a MC can give you more detail and air etc but a good MM has benefits of its own. A more solid, punchy sound with believable weight. A lot of people run good MM carts by choice and not because they couldn't afford a MC.
What is the deck and tonearm?