I don't know what rain pants are available in UK or Ireland. Here we have all kinds, but not sure about ones with leg zippers all the way up.

Most of mine zip up to maybe my knee or bit lower. I'm only size 9 foot. But here is how I get them on:

You DO have to sit ... which is a drag in the rain on wet shitty ground ... but at least I can get my boots through the leg.

What I try to do is to crunch up the rain pant leg like you would putting on a sock, then work it over your boot, one boot at a time. Yes, bit of a PITA.

I must have 5 different pair of rain pants. I find former ski wear in thrift shops and such. I do have a new pair of Frog Toggs, which come well rated. Not used them yet!

Most of mine will eventually leak in crotch if ridden in rain all day. But they do a good job over all for an hour or 3.

Most all the companies that make riding jackets and pants offer rain pants as well. In UK you've got Halverson's. Good eh? But look pricey. Dunno.

Here we have: First Gear, Joe Rocket, Tour Master, Alpinestar, Aerostich, AGV, Fieldsheer, MotoPort, Bilt and Sedici (Cycle Gear) and several others.
Not hard to find in shops or online. The very best? Who knows!!!

Just keep shopping, I'm sure you'll find something that works. Mine tend to get torn up traveling, but usually never pay more than $10 to $15 usd for them, so no big deal. Expendable item!