Bek suggested that we could make our own glue from flour and water. I have fond memories of my parents making this for us, when we visited our Grandma, who wasn't as well stocked with craft materials as we were at home. I looked about online and made up a recipe based on several different versions that I found.
I put two tablespoons of flour and one teaspoon of sugar into a saucepan, then added water gradually over a low heat, whisking continually. It thickened very quickly and became very lumpy, but by adding a bit more water I managed to make a paste. I gave it to the children with our usual glue spreaders, and to my surprise it worked really well. It stuck nicely, and would be particularly good for large scale gluing projects like papier mâché. It went lumpy as it cooled so you'd need to make it fresh each time, but it was definitely a success.
Yes, Mia did eat quite a bit of it, but I tried a little bit myself and it was actually quite tasty so I don't blame her!
Bek also reminded me about homemade playdough. A little while back I found a great non-cook playdough recipe from The Imagination Tree for chocolate playdough, which was easy to make and very successful. It's still very salty, so you need to make sure that a child doesn't eat very much of it, but it must be better for her than the commercial alternative.
Paint and edible messy play
I found these sachets of custard powder and flavoured dessert mix in Asda, they were no more than 14p per sachet. Sainsbury's also do similar versions.
I made up the custard powder with hot water as per the instructions and the dessert mix with cold water (if you were making it for an actual dessert you'd use milk but that's a bit of a waste when it's just for playing with!), and I put out a selection of different things to use with it.
Among other things we used bits and pieces from the toy kitchen, cars, ice cube trays and paintbrushes. It kept them both entertained for a very long time, and after that they both went straight into the bath, making this a fantastic activity which kept them happily occupied for an entire morning. It was a resounding success, and an activity that we have repeated several times over the last week!
So if you are experiencing the same problem that I am, I hope that you have found something here to inspire you while you wait for this phase to pass!