Possibly tempting fate, but have short checked bags to LHR (CX did ask if I was sure I had enough time when doing so!) and booked airportr to deliver my bags home later that evening - £34 for 2 bags with a discount code. Their arrivals desk isn't open that early but departures desk is - and is on my way. There's plenty of Avios availability on the later flights from FRA so not running a risk there (I think...)

Will see how it goes.