I brought some tiny baby plants back from Cornwall with me in Feb to get a head start. It worked well last year!
Then sowed mine in March, heated propagator indoors. I heated the greenhouse to put them out to 5, then gave in & put it to 10.
They did then go away with me & were put in an unheated greenhouse for a week end of March, which may have checked them a bit. They weren't potted on too quickly because I knew I needed to transport them. No food until first fruit sets.
Still, I'm in West Sussex & am disappointed that mine are so far behind yours in East Yorkshire Johntheeng!