Playing around with the website, you can get GBP39 from LCY to EDI for example. A One Way the other way round prices out the same. But I have been getting stupid things, such as the flight arriving at an unrecognizable time +49 days, or +322 days. I mean, these really are stupid things on what is supposed to be a serious website. I surely cannot be alone in getting progressively p***ed off with rubbish websites, overloaded with useless graphics, full of bugs, and never working properly?
If you price out a Round Trip starting in LCY, some pretty good prices come up (GBP39 outbound, GBP 24 inbound). If you price out a RT starting in EDI, it is more (GBP 40 outbound, GBP 56 inbound). So if starting in EDI, it is better to book two OWs. I haven't checked DND yet, which is closer to where I want to go.
As for my own trip, I booked easyJet from GVA to AMS for CHF45, and then a special 5,000 miles tkt on KL from there to EDI. I was on the point of giving up and boycotting Sleazy for good, because it took 4 attempts to push the booking through on that stupid piece of rubbish of a website of theirs (but that will be the subject of a rant elsewhere).