The length of the lease would probably put me off. Obviously allowing the lease to get to 80 years is a huge no-no, but prices can start to creep up once it gets below 90 years. We extended our lease recently. It cost around £5k and we didn't need to use a solicitor.
We put our one-bed gardenless flat on the market at the start of this month and sold it in two weeks. However, we were fairly ruthless.
We hired Big Yellow storage and decanted about 2/3 of our books into it. We were discerning with the ones we retained.
We got someone to look after our pet while viewings were going on and removed all traces of it.
We removed much of our clothes, crockery and truly personal items (family photos, pictures and trinkets that were meaningful to us but not anyone else) and put them in storage too.
We didn't remove all personality from the flat, but we presented a curated version. We had a very specific type of buyer in mind (young, single, aspirational professional ftb) and ruthlessly targeted that sort of buyer. For instance, we kept the Lonely Planet and Rough Guides on our bookshelves, along with pictures of foreign destinations, because we wanted to give the impression that the type of person who lived in our flat was well-travelled. I decluttered all perfume/aftershave from the bathroom except one bottle each of the most expensive because we wanted to show that the type of person who lived in our flat was well-groomed and able to afford expensive products. It sounds silly, but it worked and we got exactly the sort of buyer we were targeting.
OP it sounds as though you're leaning towards staying put. However, if you do decide to sell, I think you can reduce the amount of stuff on display without losing the personality. You want your flat to say 'the type of person who lives here is Bohemian and creative and able to live in central London'. However, it needs to be depersonalised. People need to envisage that they are the Bohemian artist living in the flat, not that they are in your flat.
Sell them your lifestyle, not your actual life.