Think i've got this down to 3 possible switch that meet the requirments:-
(rough pricing 🙂 )

2x Ubiquiti EdgeSwitch 48 Port - £920ea
1 pack of 10G Transceivers - £35
2x RJ45 10G Transceivers - £62ea
Total - £2000

2x HP 1950-48G - £1230ea
2x 10G-SR Transceivers - £600ea
*Don't need any Transceivers for the one in same building as it as 10G copper already
Total - £3660

2x Netgear S3300 - £1020ea
2x 10G-SR Transceivers - £238ea
Again already has 10G Copper.
Total - £2516

I see we can get "compatible" Transceivers to reduce costs to:-
HP £16ea - £2492
Netgear £13ea - £2066