Thank you sleeps :) I'm using Instituto Bernabeu. They've been ever so good. I haven't had to go out to Spain yet, they do the initial consultation by skype. They put me on a treatment plan that required a uk scan at a clinic of my choice around day 10-12 of my cycle then based on those results (the clinic did me a report and scan photo printouts to email across) they gave me a date for the transfer.
This time my side effects have been migraines and extreme tiredness, but it's completely possible that I would have had that anyway, as it's not been every day.
Technically we only need to be in Spain until after the transfer, but we've decided to make a really good holiday out of it and are staying over for 12 nights. The process was ever so quick, I contacted them the cycle before last, had the skype appointment at the start of my last cycle and am having the transfer this cycle.
Essentially it is just FET, but if the embryos they have selected don't survive the thaw they are able to just choose more from their freezer as we aren't genetically tied to any of them.
They match as closely as possible on physical characteristics, and you can give (I think) up to three things you want them to give high priority to. I asked for the donors to be taller than me, because I hate being short 
If I were to have one emby transferred they reckon the odds of success are 30%, and with two being transferred the odds are 50%. The donors are so young - average age of 23 for both male and female, so they really are at their peak for fertility.