Big hugs, @CathyMac - I can feel your heartbreak and the silence in the house would be deafening. It is all compounding in the one hit. .... the BC, the lost holiday and now your son flying the nest .... so your sadness is not only normal, it is expected.
I hope you are able to factor some visits in when you are able ... and in the mean time, there is Skype and FaceTime .... he can walk you thru his new ādigsā so you can see them first hand and meet his flat mates .....
all the best xxxxx