I've just tried to ghetto one of my tyres this morning, it inflated fine with a track pump, no leakage from around the rim, but there appears to be a bit of air bubbling out of the sidewalls in tiny pinprick bubbles.

Would this mean I'm looking at a ghetto Fail with these tryes?

Keep them topped up, they'll either seal of they won't.

HTH

Contis?

They will settle down over a couple of days, just keep re-inflating & shaking every now & then

Maxxis Ignitors, I'll give those tips ago

Assuming I get no further air loss after the initial steps, how soon is it safe to ride, straight away?

IME riding straight away helps to seal them, assuming they are only loosing air slowly.

Nice one I'll have a spin up & down the road

Follow the instructions.

Lay the wheel flat a top a bucket so the sealant pools on the sidewalls and seals them properly. Takes a few hours per side.

The instructions I'm following don't say that.