We had one or two cold nights, other than that it hasn't been too cold here, near the Peak District, probably been a bit colder & wetter on some of the hills. I haven't started looking yet, they don't usually really start coming out until mid-september. I've seen a few in July & August before, but just 4 or 5 usually, not found enough for a trip before september before, but looking at the shroomery it seems it's worth a look. I suppose if it's been damp & 5-10 degrees C for a few nights in a row then it's worth looking. At least it's a nice walk in summer even if I don't get any.
I find they're easier to spot if it's dry & sunny, shortly after a cold wet spell, it's better light & the mushrooms are a lighter colour, there aren't as many as later in the season, but they're easier to spot. Looking for tiny wet muddy dark brown mushrooms in a wet muddy brown field in the rain can be tough until you get an eye for them, I often wonder around for half an hour before I find any & then they all pop out at me.
I never found any below 200m either, but early on in the season it usually needs to be bigger hills, like 400-500m+
I try to spread the spores a bit too, not managed to start a patch in my back garden yet, but I'm sure I seeded some bowling greens in the park one year.
If it's your first time shroom hunting then please go with somebody more experienced until you're confident you can identify them. I don't think there are any deadly mushrooms that look anything like liberty caps, but there are a few similar looking shrooms that might possibly make you a bit ill & inexperienced wild mushroom pickers have sometimes picked deadly mushrooms (I think it's usually people looking for edible mushrooms rather than libs though). There is good information on the shroomery, but it's not a substitute for experience. Need to check they're the right shape (nipple on top, etc), size, the gills/spores are dark, thin wavy stem, right colour (between light beige & dark brown, depending how wet they are).