Have had the quotes back now from a third supplier who did a site visit on Monday and I will be going ahead with this one. Aside from a better price than the other two, they have also given me a much more detailed quote than the others did.
They have recommended either a Rolec Homesmart 20:20 or Ohme at the same price, both on a tethered basis for less than £900 after the OLEV grant. This is about £150 - 200 better than the other two for a non-Tesla charger.
In my case, a cable run of around 40 meters is required and whilst it doesn't add an enormous amount to the materials costs, it will involve a certain amount of faffing about to run the cabe. Our meter cupboard is at the wrong end of the house and we have a detached garage.
Happy to share more details if you are interested, but this is the firm I am using (Cheadle based)
Electric vehicle charge points for home use - Eco Charge Points UK
I have no connection with them other than as a new customer.
As an aside, I also approached a local 'traditional' domestic electrician who agreed to quote for the Tesla charger installation. He came out and had a look at the job, took details of the Tesla charger and I sent him a link to the installation instructions and technical guide. He never came back to me.