Apologies there is an error in my calculations, thank you for pointing that out, I have multiplied the no. of seats available return by the total no. of flights instead of the no. available one way... So, 2 752's, swapped for 2 738's (although I think the plan may be 3 now but my calculations were based on 2)
752 = 235, 738 = 189, 235-189 = 46
46 x 2 = 92
2 returns per day per aircraft = 8 one way flights per day +/-
A/C 1 = 46+46+46+46 = 46 x 4 = 184
A/C 2 = 46+46+46+46 = 46 x 4 = 184
184+184 = 368 seat deficit. Still quite large.