I don't think anyone can comment on specifics about price unless they're versed with up to date local knowledge.
@Veebie86 this house appealed to you and you chose it. You know its strengths but they're not really coming across in the marketing and this agent's photos are all very poor.
Reading the thread people think it's a lovely home and well presented, but talk about the negatives already discussed like the clarity of the mezzanine space and where the actual space is to park. They're big issues to address.
I agree with PP who say go with a local agent and agree together how best to appeal to your target market, which would be just about anyone apart from a growing family. There are plenty of people who go for the charm and quirks of period properties and who sacrifice space, a driveway and energy efficiency, you just need to find them and entice them to look for themselves. Some people buy with their head and others will still go with their heart depending on their budget. See you've agreed on this since I started typing ages ago and the Open House Day idea too.
Personally I wouldn't change the Orangery roof as the dining area looks a bit dark to me. Presume its window is close to next door's tall wall. I may look at some insulating film for the Orangery roof and the velux windows to help the EPC a bit and perhaps some film which would still allow light in the dining room but screen that wall out? Not sure how fiddly or effective that is, but it is something you could do. I really wouldn't spend much on the house at all as you likely won't be getting it back.
By way of anecdote we once struggled to find a new home and after forging a good relationship with an agent, they took me to view a property I'd never have considered and yet loved. When we came to sell we went back to the same agent and secured a sale immediately to someone who's own home he had on the books under offer from a first time buyer. Absolutely no fuss and it all went through sweet as can be. It can happen and after all, you only need one buyer.