Mullerlights are all free unless they are the layers ones or some of the chocolate range - see the threads on the syn forum for more details.
If you mean jelly crystals (which you add hot water to), Hartley's sugar free sachets are 1.5 syns each (same for supermarket brands I think).
Meringue nests - average of 3 syns each according to website. If you want more detailed info, let us know the brands or weights.
Hope this helps! Sounds a tasty combination anyway....