Muck boots were excellent but expensive, and they don't seem to stock the ones which were best for me anymore, however, I also have some 'Dirt Boots' which are one option, as they do not fit quite so perfectly as the Muck Boots it is advisable for me to wear a slightly thicker sock.
A lot depends on the terrain you will be walking over, around here it is sloping, slippery and the clay/chalk mix will clog up most cleats so I tend to have to buy at the more technical end (mildly more expensive) where the cleats will cope. Small, closely spaced or regularly lined up cleats are great for sliding and damaging your back, but not for walking around here, if it was peaty bog, cleats don't matter so much as leg length does (Scottish bog in your boot is not nice). My cleats are also OK for dryish or hard edged rock.
Having damaged an ankle last year the Muck Boots were too good a fit and the Dirt Boot option was a good solution. Because I have fairly well developed leg muscles I find full height boots less comfortable that the 3/4 size (I appreciate keeping the circulation to my feet!)
Dirt boots and many other good options are on Amazon, which does mean that if you buy a pair and you can't get them on you can at least return them easily.
Tried out of curiosity to google Welly boot reviews and no one seems to agree on much - good luck!
The best advice is really to go to a few outdoor shops and try a few on if you can, a bit like binoculars really.