When DH was staying in the States with me, we tended to shop at The Pond Hopper in Fort Lauderdale, FL. The owner was super friendly. It was quite a drive, but we always made a day trip of it. I think he also has a website. 2629 N Federal Hwy, Fort Lauderdale, FL 33306
Orlando, FL has The British Shoppe. You can purchase online or in store. 809 N. Mills Avenue Orlando, FL 32803
We were recently back in the States and the Publix in Naples, FL actually has a British food section. The only thing they didn't seem to carry was golden syrup.
One unlikely place we found some British food was a small Greek shop called The Daily Bread. It is located south of Miami in an area known as Pinecrest. 12131 South Dixie Highway Miami, FL 33156
Oh yeah, and TJMaxx had tons of Walkers shortbread.