I would certainly steer clear of www.ultraonlineuk.com
#1 tell tale sign, out of date SSL certificate. I.e. a no-no for any e-commerce site.
As for www.tecobuy.com it seems better, it is secure - but not risk free. As others have mentioned it is based in Hong Kong, so the name of the website is a deliberate ploy to lure customers under false pretences. Delivery would be hit and miss at the best of times, e.g. expect a 4-6 week wait. But with the current climate, I wouldn’t even bother.
https://www.scamadviser.com/check-website/tecobuy.com
Tecobuy seems like Alibaba, Aliexpress and Banggood’s little brother. Yes, they are cheaper, but there are risks involved. Fakes are common place, items take ages to deliver (if delivered at all) and the returns process is sponsored by Cadbury’s Flake.
My advice, even though the MM2 is advertised for £490 on Tecobuy, I would recommend paying the extra to get it from a reputable dealer, for peace of mind. That way, you know it will be delivered and within a reasonable timeframe. But you will be in a better place in the event you need to return it.