Some popular pots with plastic microwavable lids:

Bottom, Evernew 0.6L, top from ziploc 2 cup bowl container.
Top left Evernew 0.9L with Glad 4 cup container top.
Top right: snow peak 600 ml pot with top from 1 cup ziplock bowl container. This one also fit the Jetboil Sol Ti and is much lighter than the jetboil plastic top.
There are loads more combos as well, all lighter than the other options. In the UK you may have to investigate what is available there. Might want to avoid plastic from containers not specifically rated as "microwavable".
These are easy to mod in seconds, are inexpensive and you can make a lifter using aluminumized tape. I usually do that and cut of the existing handles to make the whole thing more cylindrical and easier to fit into a stuff sack. You can even use the original container, with shared lid as a re-hydration/eating bowl, if you like.