My chillies, tomatoes and cucumbers still have a little bottom heat. They won't go out into the tunnel until after June 1st - even then it can be bloomin' cold here, so we will cover them with heavy duty fleece at night.
I'm just about to sow courgettes and squashes, which mean they are ready to go out on June 1st before they outgrow their pots
It would be too late to try sowing tomatoes and aubergines now, as they need an early start, so you'll need to buy more young plants. It's a nuisance, but you'll know next year.
I think your plants will also have had some heat before they were sent, so needed to be potted on and very carefully hardened off to conditions in the tunnel. A tunnel only raises the lowest temps by about 1deg C, although it does keep the wind off. To test the soil temp, scrape the top off a bit and place the inside of your wrist onto the soil. If it feels cold, then it's too cold for delicate plants (you can also use your bare backside, but the wrist is fine
). To test air temp, get a max-min thermometer - it's worth the money to know min night time and max day time temps.