Sweet peppers grow best in a greenhouse, polytunnel or conservatory, but will also grow outdoors in a very warm, sheltered, sunny spot (at the base of a wall for instance),
Peppers like warmth, so wait to plant until nighttime temperatures have consistently reached 60 degrees and all danger of frost has passed.
March to April in modules on a heated bench or in a propagator at a temp between 18 and 21C. Transplant to 7.5cm pots after 4 weeks. Plant in final positions indoors no earlier than May.