I personally think 75k is a tad low on this to be fair

But the days of 150k are gone for now that’s for sure

Suspect a fair price for all is around 90-95k

Well, it's not June anymore. How much did the seller receive?

Price update: £125k 

No one is paying £125k for the GDP version after the auction season we had, I would be surprised to see £100k TBH. You got it for £500 dude, you missed the boat for the big money but its still 20x in 4 years , don't ride the market down for another year, offer it at a fair price, take the money and enjoy life. If you want to hold out for 5 more years then who knows but I suspect there are far better places to put the money for 99% of people.

contact  an auction house , the major one will accept it.

Set a reserve price , accept the fees and sell it (if you’re really interested into selling)….

The resale agreement from GDP? GDP was 5 years ago. I would like to hope most GDP buyers have coas by now.
Resale agreements aren't an issue. Pest Controls greatest mistake is absolving themselves from any responsibility past the point of primary sale and directing everything(unique/rarities/original, main ed) to auction to resell, effectively passing the buck, making the auctions the current market management. 
That's not what auctions do, they sell, as much as possible to keep shareholders happy at the end of each quarter. Banksys future market clearly isn't a great concern for auctions. It's not their job.
 It used to feel more of a community, everyone looking after the artists and markets best interests.
 Now it feels more every man for themselves, especially with Pest Control Office and the artist.
 Sellers think for yourselves. If you're out of options outside auction and have no choice but to sell right now then go to auction and take whatever you get, most likely it will be 1 bid, bottom estimate or below. Or no sale.
 If the seller isn't in a panic to sell, holding long term might be the better option. The GDP triptych is a work many will want once there's some confidence instilled. Where the confidence comes from and when isn't evident presently which is causing uncertainty. It certainly won't come from the leadership of PC, they aren't sending the right signals out at all to settle concerns.
 First action should be  PCs staffing issues. Are more staff needed? Is it a staff efficiency/knowledge/expertise issue? Or both. What can cause such long delays in communication/coas etc leaving collectors stranded, stressed and helpless for years. If it's sheer volume get more staff, get them trained. If they continue in the same vein they will make it hard to convince collectors he's a good option for spending their money.  
 It's ultimately down to the artist and whether he cares about his collectors. If he doesn't care about his market/collectors that's fine, but he's picked up the responsibility along the way so he has a duty to at least put the right staff in place that will care or are capable of managing his market with some level of credibility.
 
 
 
 
 

GDP shipping was delayed for a year, then COA's were delayed for a year.  So most COA's were released in the last year.  I'm pretty sure everyone has them now, hence the influx of prints on the market.  Mainly smaller galleries are listing it, who require the COA.

Lets be honest its not just Banksys market that crashed atm, almost every artist is noticing a very significant dip at the moment.  Even think Thierry Noir might go to zero.  (bait)

Can’t see Ukraine, Middle East or other world problems sorting themselves out any time soon.

Are you saying you are waiting for your GDP COA?

Sorry to hear, hope they sort it quickly, are they being the usual non-responsive?