I've heard an 1/8th of an ounce is between £150/£250 depending on where in the UK you live.
It's all shit these days anyway unless you use the DarkWeb/Bitcoins and take your chances getting some proper fish scale stuff delivered to your door.
If you wanted to there's serious money to be made doing that as the quality is Really strong so you can cut 1g into 3g and it's still gonna be stronger than 90% of the shit people buy these days.
The Government are seriously clamping down on it now and have dedicated police teams just to target the Darkweb drug problem in the UK.

It's a massive problem but in my opinion the lesser of two evils because as far as i'm concerned people will always take drugs of some kind.....
Alcohol, cigarettes (both do way more damage than any "Illegal" drugs but are a huge tax earner so that's ok)
At least people know that their product is pure if purchased from sites you can find with a bit of research and not full of unknown "legal high" cutting agents that seriously fuck people up.