@judith I would think Octopus are more likely to hand over the jobs in areas with no fitters. It's a massive problem around the country - my Octopus guy told me this and I've seen people online saying they can't get an Octopus installation. You can't get Heat Geek installers in many places too or else the waiting list is miles long. 
On the policy side it's an example, not party political but a general government problem, of not having a clue how to plan and roll out mass installations beyond bunging a grant out there.
In the old days.... (😁) the local tech college would've been rolling out low cost City & Guilds 'Heat Pump Installation' level 1/2/3 etc., System design 101 and so on with on-the-job training thrown in.
The unemployment benefits office would push their brighter candidates in that direction with promises of keeping their benefits while training. There would've been 'public information' adverts on prime time TV on the wonders of heat pumps. 
I'm showing my age here but the demise of the good old fashioned Tech College has had endless bad effects - primarily in terms of training and up-skilling but also in their social function as the centre of communities. It's driven me nuts for years but at times like this when we need installers and mass roll-out of green energy policies it becomes very clear. 

@judith Octopus eventually turned me down on the grounds that they will not do any install that requires them to do work on any roof. The only viable pipe paths are over a roof, so they are withdrawing. Other installers don't see it as a problem. So, at least in my case, someone else gets an easy install.

A Heat Geek installer came to assess my house today. What a difference from the other surveys, as in the professionalism displayed. He was here for 3 hours, asked many questions, scanned each room and calculated the heat loss. I need a 12kw HP. Interesting when I compare that to previous surveys by Octopus and others who said I needed anything from 8kw to 14kw. What was also interesting, and no other surveyor pointed out was
The proposed location of the HP would need planning permission.  
One of the bedroom floors would need to be taken up to replace pipes to the hot water tank with larger bores (effectively meaning a new floor would need to be laid) adding to the cost. 
A comms cable ditto above.
It would take between 5 to 7 working days - so without heating for that time. Not a winter project then. 
I’m now waiting for the quote.  
 
 
 

@davesoa
Did he have any comments on your existing radiators?
I've already concluded that I will probably need wider bore 'tails' in the airing cupboard from where the boiler presently is to where the plumbing T's into the two sides of the house (maybe 2m).  Also a section to the adjacent bedroom en-route to several radiators (maybe 3m).

@ianmk13 Yes radiators will need replacing, most if not all. Many of them were installed 30 years ago and the plumber basically guessed the sizes when he installed them. However Octopus (and the others I consulted) also said I’d need replacements so I was expecting that.

@davesoa
My radiators appear to have been well-specified for the total house heat loss, but at ΔT50. I'll be needing to replace all mine, too.  At some point, the gas boiler was replaced with a ginormous beast by BG.  It hasn't aged well, with the ceramic burner having to be replaced last year.  I suspect because of short-cycling as it couldn't modulate sufficiently low.  When I moved in it hadn't been downrated and the flow temp was set high. 

Received my Heat Geek quote this evening. Very detailed, well laid out, clearly explained, guaranteed efficiency of 390%…and eye wateringly expensive. As in more than three times the initial Octopus quote and twice as much as EDF and two independent installers quotes. I realise that’s academic as Octopus declined an install. On top of that I would need planning permission for the HP and replace a wooden floor (initial estimate £1k) for new pipes to be fitted. I will decline it. The consultation fee is fully refundable. 

@davesoa 
I was led to believe the survey was non refundable but would be taken off the cost if you went on to have it fitted with them?
I eventually declined the £375 survey fee from a local heat geek as he only answered emails weekly.

@njt I quote from their terms and conditions at the time of agreeing (and paying for) the design consultation.
‘After your Design Consultation has been conducted, you will receive a detailed proposalfor the works to install a renewable heating system at your home…Up to 30 days after youhave received your proposal, if you do not wish to proceed with the installation, you mayrequest a refund of the design consultation fee. We will process this request within 20working days from receipt.’

@davesoa 
Thanks. 
I went direct to the installer, maybe that was the difference?
Did you go through the heat geek website?

@njt Yes I did. I thought (suspected) there would be an upwards adjustment to the final price as a consequence but knew, if I didn’t like the proposal, I could get a full refund.

I went via the Heat Geek website and had the same T&Cs saying the fee was refundable. I'm yet to get the refund after declining my proposal which I need to follow up, especially as I got an email asking me if I still wanted to go ahead and if so to let them know as there was a problem with the installer.