Best ovulation tests/kit?

I have very irregular periods(very late or very early)

I’ve used OPKs before, and I got the hang of it but then stopped cause I thought I was stressing myself out more..

I want to start the OPKs again, but what ones should I get? Where is the best place to get them from?

I’m in the UK, and also going through fertility testing atm..

9 years + TTC, I’m just so ready to be blessed now 😩

TIA 💖