When people say £1 a window, is that £1 for a large bay £1 for a frosted single pane bathroom window? It doesn't make sense to me to quote that method.
ok example say a big ish 4 bed house with a average sized con.
has a large ish front door £1
above that a small kids bedroom £1
large bay window - living room £2 - £3
large bay above - main big bedroom £2- 3
small door glass on side and small en suite window above - £1 - £2 for both (depending on size say)
round the back 3 tops
two bedrooms - £1 each
patio door £2
kitchen window £1
very small glass on door ( call it a £1 with the small bathroom window above)
then the con £5
so that say £15 - £20 for a large ish 4 bed house with con.
depends on clean frequency etc ... but you get the idea