drainage will still be at the bottom but will be facing inwards so will probably need to seal up the existing holes and redrill new in sashes and bottom of frame
I can quote supply only either aluk or origin doors.
No dpc needed just sit the door on a good squeeze of sealant and put an add on to the side of the door
It may well not have a thermal break in the frame as it looks like commercial aluminium apart from the doors. Its 100mm x 50mm curtain wall with a pressure plate by the looks of it.
Generally get the heritage style locks on composite doors. So you use a key only to unlock the door from outside and a thumbturn no key needed on the inside
Get down to b and q and buy a screw on rubber strip
https://www.ironmongerydirect.co.uk/product/exitex-perimeter-seal-single-door-kit-plain-aluminium-883784?vat=1&shopping=true&gclid=EAIaIQobChMI3-GZ2bf64AIVg7DtCh2zbwBcEAQYASABEgJD8_D_BwE&gclsrc=aw.ds