I am curious to understand your experience of these malts. The ones you do or don't like: can you describe what about, e.g., Dingemans, Munton's, or Crisp MO, really stood out for you (as good or undesirable)?
Simpson's ticks all the right boxes for me, both GP and MO. The malt flavour, the colour, efficiency, etc. They're very flavorful, but not overwhelming and well-balanced. Munton's is similar, but has a more intense flavour profile. More malty and other terms I'm not good at describing regarding malt flavour. I like that in dark beers a lot, but sadly I don't have a supplier anymore. Crisp is not bad, but it seemed to have less character and the flavour was not as full. Crisp also has a slightly lower yield that can come into play when brewing big beers. I've used it mainly in dark beers and it just wasn't the same as Munton's.
Fawcett base malt is also rather lacking and somehow the MO seemed a tad astringent. GP was decent, but not as good as Simpson. Mild is a very interesting malt though. Halcyon I've tried once in an imperial stout and that beer is weird. I'm not sure if it's the halcyon or anything else, but it's a recipe that's similar to what I make more often so I'm leaning towards Halcyon. I do really like their crystal and roasted malts though. Dingemans MO was full of DMS, too light for me and lacking in flavour. Their wheat and Vienna are nice though. Paul's is plain, boring and too light for me. I don't like most of their malts I've tried though, because they just don't seem as flavourful as other English brands.
Viking Munich was the first Munich that I tried that has a good depth of flavour, strong backbone and a potential good standalone without overwhelming me like the extra dark Belgian stuff. I used Swaen before and their light Munich is very lacking in flavour and their dark Munich is more of what their light Munich should be. I don't make a lot of beers that are full on Munich so my references are somewhat limited, so perhaps Viking is the odd one out here, though I wouldn't think so purely based on the colour Swaen's have without the flavour backing it up. Like I said, Belgian Munich can be super dark, but it also tastes equally intense.
I haven't had the chance to try Simpson's crystal yet, but their roast and base malts are awesome. Crisp is also amazing for roast malt. TF is good for mild, crystal (medium, dark and especially extra dark) and roast (especially black and rye).
Edit: I also just realised that I have DM Munich now, but I'll need to do a SMaSH with it. I've tried it together with Weyermann Munich 2 in a rauchbier and the malt flavour is spot on in samples (it's still a bit yeasty), so I think I would like that one as well. I'm leaning towards Swaen being the bad option here, because when I used their Munich there was a lack of maltiness in pretty much the same recipe otherwise.