UK b12 pills not methyl?

So had my bloods done about 6 weeks ago, showed low ferritin (13), low vit D (61) and low b12 (199). All within range according to the NHS but I managed to get some ferrous sulfate prescribed.

I've been taking that and some vit D but my anxiety has skyrocketed to ridiculous levels. Im now back on propranolol to try and manage that. I tried about a month ago to supplement b12 but it made me feel absolutely awful, never had anything like it before. After browsing reddit I find that I'd been taking methylated b12 and im assuming it's that.

Does anyone have any experience with cyanocobalamin pills that aren't super strong in the UK? Maybe also if you've had a reaction to methylcobalamin. All I can seem to find is really strong b12 cyano and I'm super sensitive to anything so want to start off with a baby dose to work up because I can't stay like this, I've got 2 young kids and a baby and I'm struggling to even get them sorted, its taking over my life.

Sorry for the paragraphs. Also I have been through the guide. Thank you.