That reading nook struggle is real - we had the same issue where the bay window area was basically unusable from November to March, too cold to sit there even with the heating on. My partner finally snapped after I kept complaining about reading with a blanket and hot water bottle, and we decided to replace the whole bay setup last winter. Biggest lesson: don't just go for the cheapest quote. The first installer we spoke to wanted to fit standard units without properly sealing the base, which would've left the same draught problem. We ended up choosing bay window installation  after comparing a few options - they actually did a proper survey, explained glazing choices for heat retention, and the fit was spot-on. Now that corner's genuinely the warmest part of the room, and I actually use it year-round. Worth the investment if you love that spot.