What do you think?

Try them on Friday and have some of their favourite treats to hand (meal worms are a favourite) so they will return for them 

yes, wilkinsons sell them (some places are very expensive), don't give them too many as they are a high fat food - however mine have been known to trip me over when they see the mealworm tub and have had a full tub in one go 

When I first got my chickens I kept them in their coop for 24 hours.  On the second day I made a small run using bamboo stakes and bird netting, and let them into that for some supervised outdoor play time. 

At the end of the day they willingly went back into the coop, so a couple of days later I let them into the full run (about 300 square feet).  They still went back into their coop at the end of the day so a couple of days after that I let them out to wander the whole back yard (about 1000 square feet).

I haven't needed to use treats to tempt them back in - they seem to have a very strong homing instinct once they are clear where 'home' is.  Each day at dusk they head right back to the coop.

Or maybe I've just been lucky! 

wilkinsons?? I didn't know that and I was in there last blinking week... I just bought a 1Lt tub of ebay worked out around £5.50

That works out better that Wilkos now.  Their worms have gone up to £2.80 for 100 gms but still better than Asda or Crocketts.  Morrisons do a 70gm pouch for £1.99.