Hey there. I'm so sorry for your loss.
I had a missed abortion last July. Like you, they also didn't find a heartbeat. I had two different scans to confirm it. They asked whether I preferred a pill or surgery and I wasn't certain at first. But I chose surgery despite never having surgery before. They gave me pills to bring home, that I was supposed to take a few hours before the procedure.
As I returned home I felt terrified I had made the wrong decision, perhaps it would be better to deal with it myself. What if I reacted badly to the anesthesia?
I got an appointment the following day and with some convincing from my DP, decided to follow through with it.
I went there, waited til it was my turn, got dressed in their scrubs and waited again to be called in. They all greeted me very kindly and shook my hand.
I laid down on the table and the nurse held my hand as she asked questions about my life. I am forever grateful for her because I was so frightened. They had a little trouble finding the vein in my hand but after that it went fine. It wasn't painful.
I passed out and woke up. I was quite nauseous and a bit crampy and very upset. I was sobbing, which made them bring in my DP.
I bled a bit for a little less than a week. The pain wasn't bad at all. Just like a period, it could be handled with ibuprofen.
I would choose surgery any time. So I think you've made the right call. My experience was "good". I'll especially remember the kind nurse.
I'm pregnant with twins now, here 7 months later, and should I lose them too, I'd pick surgery any day.
(to be fair, my treatment was at a Danish hospital, I don't know much of the nhs)