Allow €5,000
Take out the garage door and anything else in the garage and dispose of it yourself €350 for skip
Order blocks, sand/cement (premixed bags handy for small jobs), timber, insulation, plasterboard, nails, plastic for damp proofing, window cill, window board, max €800
Window €500
Blockwork pay day rate €250 euro if you can find someone, very easy job if you leave the window the width of the door.
Plastering in and out anything up to €600
Electrician €400
Handyman/carpenter for dry lining walls and ceiling €800
New floor in extension (may need to be raised) ????