Hardening off any plants before they go outside is important as they need time to adjust to sunlight, possibly cooler temperatures and drying winds.
Move the plants outside into a shady spot for increasing amounts of time each day but bring them inside again if the temperature starts to fall. Gradually increase the amount of time they spend outside and the amount of sunshine they receive.
Once all risk of frosts has passed, water the seedlings well and transplant in the morning or when its not the hottest part of the day.
Its probably some way off yet that these chilli plants will be promoted to the poly-tunnel as the forecast for the week ahead is saying snow (from summer to winter in one week!)....and the poly-tunnel temperatures at night are dipping down too low for the chillies to be comfortable with, but still, it was nice to get the chillies out, breathing in the warm air and enjoying the sunshine with the rest of us.
Hope you all have a good week...wrap up warm!