Develop commercial window cleaning customers - South Wales

I hope to start a window cleaning business in South Wales, wanted help to grow this. This is in the early stages of planning but I wanted to check if anyone had experience of growing a window cleaning customer base? I guess it would mean targeting commercial customers? I hoped to canvass domestic customers but thought maybe a professional could deal with businesses? I also run a carpet cleaning business so wanted to use this as an enticement to become a window cleaning customer ie discounted/possibly free carpet cleans for customers who use me for say 12 months.