So we sold our house in August, with our sellers offering us the full asking price on the proviso that we completed ASAP. We were happy with that as had offered on a property (private sale, no EA) where the sellers were separating and wanted (apparently) a swift conclusion. The seller took a month or two to find a property, and then on do doing locked us into an upward chain of about a further 3 properties.
Since the start of the process our seller's solicitor has been interminably slow, not completely responded to queries, omitted paperwork, and just generally takes three times as long as necessary to move things forward.
We've also had lots of changes going on at the upper end of the chain and just before Christmas the upper link of the chain (I think link number 7) pulled out of their purchase snd started to look for other properties.
Both we, and our buyers were in absolute despair at this point, so much do that our buyers said they'd be asking their solicitor to write a stamp duty clause into our contract.
Initially we were relatively relaxed about this, as we thought we had sufficient time to complete before April 1, and in any case we'd ask our seller to agree to the same terms to protect us and also as an incentive to progress more quickly.
Anyway, to cut a long story short, our seller 'politely declined' this offer. Therefore, due to the value of our property and the one we are buying, this would potentially leave us liable to about £30k in stamp duty over both properties, if we agreed to our buyers' request (to save the purchase) and then also had to pay the SD for the one we are buying.
Prior to the stamp duty request being made by our buyers, we had asked our EA to float breaking the chain with our seller to see if we could get moved before Christmas. She also refused that offer, and refused the offer even when we offered to pay all of her costs to move into rental.
Just before Xmas, link number 4 (so our seller's seller) clearly got fed up with all the messing about at the top of the chain, pulled out of their purchase, thereby chopping off the top part of the chain, and have since found a property with no onward chain, so we have everything crossed that we can get this over the line before April.
I have been in despair so many times over this move, we have moved 3 times before this and not one of them has been anywhere near as stressful as this.
Do you have a relationship with your sellers' OP or are you doing everything through the EA? Either way I'd ask your solicitor or EA to suggest that the sellers break the chain and that if the agreed date cannot be achieved you'll expect them to pay the SD. It's just not on. I don't know if some people are oblivious to the stress this all causes or if some of them just don't give a shit!