Hello Andy,
Considering your regular shoe size (45/46) and the neoprene socks you will need size
46-48 pockets.
However, forget the fins you are considering, except maybe the Omer Millenium footpocket.
The BAT blades are totally flat, i.e. they don't have an appropriate angle where the blade enters the footpocket (normally 12-18°). Not very comfortable, not very efficient. Actually, I am happy to send you a pair of BAT 20 or 25 blades for free, if you pay for postage to the UK.
The Pegaso is
rediculously overpriced (apparently, the advertising costs are bearing down on the consumer

). At this price you can buy the Omer Records 3 under the 'original' branding
Mack VI by PVE
=>
Bienvenue sur le site d'Histoires d'eau
or even
C4 Falcons at the currently discounted prices
=>
Pale Falcon - 175.00Euro : Scubazar, Aquista qui la tua attrezzatura subacquea
If, however, you prefer fiberglass over carbon blades
Kaleidos/XXone are the way to go
=>
Pale Kaleidos - 160.00Euro : Scubazar, Aquista qui la tua attrezzatura subacquea
=>
http://www.bluworld.com/test/Scheda%...20Kaleidos.pdf
=>
http://www.apneateam.it/Fai%20da%20t...gio%20Pale.htm
I am yet to find a spearo who has managed to break them and when not having a boat available, i.e. starting from shore with lots of surface swimming and hunting at moderate depth, these are my favorites.
As for the blade stiffness (3 hardness grades to choose from for Mach VI; 5 hardness grades for Kaleidos/XXone), you would need to provide more information regarding your approx. weight and fitness level.
I hope this helps.
Cheers,
ulysses