@Bunkbedpeople and @DudefromThatLondon Thanks for your comments. It is pretty shite, and I am feeling bad, but I've had enough breakups to know how badly I usually take them, and this is no where near as bad as most.
If I'm honest I'd had thoughts over the last month or two that things weren't right, and I needed more from the relationship but I didn't say anything as I didn't want to pressure her knowing she was having a tough time. She'd even told me a few months ago that she wouldn't have as much time for me, and that maybe I should get back out there dating again, so I think the writing was on the wall at that point and it was only a matter of time.
I've also been reminded of comments I'd made to friends earlier in the year where I said I enjoyed spending time with her, but didn't think it had a long term future. It was clear that we wouldn't spend Christmas together - she was going to have relatives over to hers, and I'll be spending it with my family. I had suggested a few times over the summer that we might go away for a weekend, but that wasn't possible due to child care schedules, work schedules, and visits to her DC.
Over the last couple of months we only saw each other every 2/3 weeks, and she'd go for days before replying to messages so I felt quite frustrated for a lot of the time. Maybe I should have walked away earlier, but these are strange times, and I was enjoying our little Corona romance even though I think deep down I knew it wouldn't last that long. But I wasn't expecting it to end quite so soon, and it's still painful. But as much as it hurts, I realise it's for the best and it will give me a chance to meet someone who is more compatible.
Which brings me to Miss Walker - I'm starting to get RSI in my fingers from typing so much in my messages to her! We have so much in common it's scary - she is almost like a female, better looking version of me! We've pencilled in another attempt to meet this weekend, so my (aching) fingers are crossed we manage to meet. I'm a little concerned we won't like each other in the flesh after such a promising build up, but will try not to worry about it. So far there are lots of green flags, and absolutely no red flags at all.