I used
Eco Charge Points UK - Electric vehicle charge points for home or business based in Cheadle who were pretty good and have been responsive since, when I had a question and some follow up. Their price was the best of 3 I looked at.
Difficult to say if the price you have is good or bad without knowing more about what is involved, that said, looks to be in line with what I would expect.
On the tethered/non-tethered argument, I would go for tethered every time. Don't need the hassle of putting a wet cable away every time you use it. Leave your cable in the boot and get the tethered version of whichever charger you go for.