Just an update. I met with the consultant today, a very lovely man. He had no problem with me canceling the procedure and my long list of questions!
He said that previous cs is not a contradiction to ECV in the UK. If a hospital says they can't do it it may be because they don't have experienced consultant. He has been doing it for 17 years, around 3-5 a week and has never had a complication other than one mother who ended up with high blood pressure after the procedure and was kept in but then had a fine birth.
He said he takes each case individually. In my case my last baby was 3 years ago, a nice long time for the cs scar to heal. I have a large amount of waters, making turning much easier, and baby was somewhere in between a footling breech and transverse position, much easier to turn than a full breech apparently. He limits the time and attempts for previous cs mums and basically if baby doesn't go first time he stops. All of this made me feel real thought had gone into my case individually.
There was no pressure to make a decision today, he said to go home and make the choice I was most comfortable with, and if that was elective cs that was absolutely fine.
Sorry for the long story but I thought it might be useful to anyone that searches in a similar situation. Your suggestions helped me put some in depth questions together so thank you. I would say definitely go for a meeting with the actual consultant that's doing the ECV to gage experience, skill and complication rate and whether you feel they have paid attention to the details of your individual case.
I don't know what I would have decided but I definitely felt more informed. However my tale has a happy ending in that I had a scan before I left in case I did decide to go ahead later in the week and baby had gone head down naturally!! We were delighted.
However thanks to the comments here I am now less nervous about a cs generally and more at peace with it if natural birth doesn't go my way ultimately. Xx