I have one Tyre, and a band you could put on one of yours, I can give you. I will bring them up the first chance I have. Hoping you are all quite well I remain your cousin Bert
Cecil is Kathleen's older brother. One day in the future, he will become Will's brother-in-law.
I assume Bert is talking about a bicycle tyre.
Bert addressed the postcard to W. C. Farmer, but Cecil was A.C. Farmer - Arthur Cecil Farmer. So Bert knew that Cecil was a middle name, and assumed it was used because Cecil's first name was William like his father's. There was an uncle Arthur Farmer, who was William's brother (I'm pretty sure).
Bert Gray was Cecil's cousin on his mother's side. Cecil's mother was Annie Gray Farmer. Annie's brother was Andrew Gray, married to Jennie. Bert was Andrew's and Jennie's son.
Andrew and Jennie Gray lived in Sevenoaks, but the postcard was mailed in Battersea. Battersea is in southwest London, about 25 miles northwest of Sevenoaks. Maybe Bert lived in Battersea.
Highbury is where the Kathleen and her family lived for a while. It is in North London, about half-a-dozen miles north-by-northeast of Battersea.
Coming across this postcard as I go through the documents later on, I am struck by how industrialization made beauty available to the common man - a thought that first was given to me by Hendrik Van Loon in a book, probably The Arts of Mankind. It's long, but worth reading.