Bricked my Pico : (

Argh, I'll fix that for the next release - thanks for letting me know.

When you said bricked I assumed you'd totally fried it. This isn't the end of the world at all - you just need to reflash the bootloader with DFU as you say.

I've pencilled over the jumper on the back, I need to hold the button to bring that one to 3.3 correct and BOOT1 ends up at ground automatically on the pico?

Yep, that's right.

the wiring diagram implies that I actually have to connect to TX to USB+ and RX to A10?

It's actually easier than that, no wiring required :)

The Pico's bootloader is USB DFU, so you just run the DFU tool (in that link above) and it'll update the firmware straight over USB :)

Just make sure you plug the Pico in with the button held down immediately before running the DFU tool. I think the boards only stay in DFU mode for about 30 secs after you plug them in.