Thank you for your kind reply, I have been reading your manual with interest. Of course you are right in that I left nothing to estimate. I had not thought about the multivariate response model, I can start with that with the group median / mean from previous years imputed to some subjects ...
Slightly OT, if you find yourself without SPSS on a particular PC, one trick that works for me is to sort as mentioned earlier in Excel, save the file as a TAB delimited .txt, open with Notepad, copy all and paste in MLwiN. That preserves the variable names.
You have to use Data Manipulation -> Sort. If it is a 3-level model, specify 3 keys and enter the sorting columns in order from the highest to the lowest level (i.e., countries first, then grandparents, then children). Select all columns as an input and output in the same columns.
Suppose that the health condition of 200 patients from each of 50 GPs was observed 3 times last year. The data can be analysed as a 3-level growth model with observations nested within patients, nested within GPs (let's assume that a linear model is appropriate for this kind of data):