I'll attempt to add balance to this argument, as I've owned this very vehicle as a commuter for a little over a year.
I did circa 50 miles a day in it during my daily slog, sometimes double that if I was called in again on-call. Both the economy and comfort were unremarkable, with the MPG sitting in the high 30's / low 40's throughout the journey. I wouldn't slander it as intolerable, yes, a tad uncomfortable at times maybe due to the K-tec coilovers, however beyond that it was a reasonable drive and great fun dropping a few gears throughout the journey to open her up, so to speak. I owned an E92 320d concurrently, which got very little use as I genuinely preferred the Clio, however that was, in some regards, due to timing chain failures on the 320d engines making me petrified to turn the key. Both of these were sold during my planned emigration.
Following my return to the UK I ended up owning a Diesel Passat whilst I searched for a property close to my place of work. The Passat, a 1.9TDI was agreeably better on fuel, however when taking the current premium for diesel fuel into account, and the drop in value of diesel cars due to various emission scandals and the governments drive towards petrol-hybrid and electric motoring, the actual saving was only a lot less profound than I what I first imagined.
If you're anything like me, you'll miss the Clio very soon after it exchanges hands. Yes, it might not be the most comfortable, nor modern vehicle on the road today, however the cheap repair costs, longevity and character far outweigh its negative facets. Furthermore, believe me, when you're replacing all 6 DI injectors, coils, plugs and coding at a BMW dealership at a cost of £1800, you'll long for the days when you could swap them yourself for £25 each in a matter of minutes.
Ultimately, it's your choice, however I'm poised to agree with those saying you should try it for a few months; you might be pleasantly surprised! You've evidently pumped a huge amount of time, energy and money into the vehicle, which will be of little solace if somebody else gets to reap the rewards.
In terms of pricing, I would expect to see around £2600, which would just about cover the purchase, insurance, tax and running of a Nissan Almera or something alike.
PS I would take it back off you in a heartbeat, however the new property we moved into a few weeks ago only has 1 allocated private parking space which is currently reserved for the M4