Right so I've paid for IHS and the visa fee now, trying to book an appointment for biometrics and there are literally no free spots anywhere within 30 miles. What am I meant to do?
You just keep trying each day until you get one... it may take a few days or so to find one, and you may have to wait a few weeks for the actual appointment.
I believe they release new appointments at midnight each night (out to 28 days ahead), so you can try at that time, and maybe at other times during the night if you can.
It's unlikely you will be able to find any available free of charge appointments, so you may have to pay £110-135 for an 'out of hours' appointment. Alternatively, some people have managed to secure an Enhanced appointment for £69.99 at an Enhanced centre... which includes document checking and scanning.