Thanks for the pointers.

Even though the CE legs are J tickets there's a £300 change fee so I'd rather not go down that route. Got a bit excited and trigger happy with the mouse when I first noticed the ex-Germany deals to HKG earlier in the year without fully looking into any turn around issues at the choice of airports.

One of the other reasons for plumping for FRA at the time was direct flights from EDI (we'll be returning to EDI or GLA), albeit with LH. However I've now discounted this as it looks like a potential logistical nightmare!