I do CE using Avios quite a bit

- when there is no availability in ET
- when it's a 2h+ flight
- when I can't face (hangover) the thought of sitting anywhere other than row 1 with a seat free next to me
- when I know I'm going to have lots (ahem..."within regulation") of hand luggage and need more overhead space
- when I want something more substantial than a wrap to eat (Band 3 only).

The bigger question for me is who the hell flies from Manchester to Paris via London!?

- BA domestics and Euroflights are more susceptible to delays
- transiting at LHR is a faff
- CDG is a dump and a pain to get to/from.

I would either fly direct or get the train. From Manchester Piccadilly to Euston is 2h8m, 15 minutes to get between Euston and St Pancras, 30 minute checkin, 2h15m Eurostar direct to central Paris would be my route. Far more civilised than flying and roughly the same time as MAN-LHR-CDG.