Hi Erik
The song you're looking for is called "Standing In The Rain" and it's by Sydney Carter. Certainly recorded by The McCalmans amongst others.

Standing In The Rain
(Sydney Carter)
Chorus:
Standing in the rain, knocking on the window
Knocking on the window on a Christmas Day
There he is again, knocking on the window
Knocking on the window in the same old way

No use knocking on the window
There is nothing we can do, sir
All the beds are booked already
There is nothing left for you, sir

No use knocking on the window
Some are lucky, some are not, sir
We are Christian men and women
But we're keeping what we've got, sir

No we haven't got a manger
No we haven't got a stable
We are Christian men and women
Always willing, never able

Christ the Lord has gone to heaven
One day he'll be coming back, sir
In this house he will be welcome
But we hope he won't be black, sir

Wishing you a merry Christmas
We will now go back to bed, sir
Till you woke us with your knocking
We were sleeping like the dead, sir



Eddie