Good job that's only a short term strategy Meg 
You poor thing, how miserable. I imagine the minute you forget to remember about it, it catches and hurts.
A couple of years ago I used one of those emergency kits you get from the chemist when a crown came off when I was away for a long weekend. It's really easy to use and you only need to use enough to smooth over the rough bit, so it might do the trick until you see the dentist. It's the same stuff the dentist uses for temporary filling, so it's all above board. It cost me about £9 from Boots, but any chemist sells them, even the chemist in Superdrug. If you need to, you can keep using it until you see the dentist. Hope this helps.
I don't want to be a doom monkey, but last September I found out that I needed a root canal on a crowned tooth. It turned out not to be straight forward and I ended up having the crown removed to complete the job. To my shock my dentist told me that there wasn't really enough tooth now left for a new crown. It did sort of feel like the crowns on either side of the one that was removed were holding it in place (these were made after the one that fell out). I am a paying NHS patient, so my dentist said the only real option was a single denture or leaving a gap (it's not in a really obvious place).
We chatted about it (she's lovely) and then she said she was willing to try another crown, but wasn't hopeful it would last. So I chose the crown and was thrilled to bits. Then just after Christmas I was attacked by the dreaded winter lurgy and unfortunately I coughed and sneezed at the same time when I was cleaning my teeth - and the crown shot out of my mouth and went down the plug hole!

I know I'm looking at single denture now, so I didn't rush to see the dentist (been very poorly anyway). My next appointment is actually on the 13th, but I need to rearrange it because I'm away. This is all a really longwinded way of saying I hope there's enough tooth left so your new crown does stay on and I'll be crossing everything for you. 