It depends on the company that installs the charger, and on the charger you chose.
We got quoted (and paid) £600 including the grant, so without grant it would be £350 more. Things that cause the price to go up would be issues in your electrical installation (fuse not strong enough etc), or long cable runs that need to go through multiple walls. Usually 10m-15m and one “hole” is included, but that’s depending on the company again.
If you’re in south wales, i can wholeheartedly suggest Energise EV, they did a banging job with the charger we chose (Easee One), installed a new fuse box free of charge, and stuck to the original quote of £595.
They also fixed something with our installation, since the previous owner cut some corners apparently. All in all very happy.
One other choice you potentially have, some car manufacturers like Peugeot (i think?) include chargers (or part payment towards it). Make sure you double check with your dealership.
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.