It just seems to me that they are determined to get some cash out of us one way or another to supplement the standard installation costs
I agree however, your big mistake was wanting it on a post and then saying you will use a longer cable, which thet will probably comeback and say it’s not possible because it isn’t safe – it is, but they will try and focus on your original plan, if going off other members on here, who have had similar problems.
Can I ask why the cable must route behind the cupnoards, rather than a hole drilled outside from you meter cupboard and the cable run externally?
The problem with standard installations, rather than quoted for the job type installations, is Motability allow one hole to be drilled at source of electrictiy meter and 15m of cable clipped externally. Anything behond this is chargeable ontop of the £750 Motablity allow for a standard install. In camparison a quoted job, will include as many holes as needed, the cable routed where ever is bbest and a extra meter or two of cable if needed all in the price, which in most cases would be far cheaper anyway.
So when you take into account The £750 Motability pay + £1600, £2350 is expensive and a local electrician would do it far cheaper and you wouldn’t be restricted to Ohme chargers.
Any energy company will fit a charger onto the wall of your house from £899 depending on charger, plus you’d save a bit if you went to a local electrician.
If your not going intelligent Octopus, where compatable chargers are limited to a few, you can save more by from choosing a much wider range cheaper charger chargers.