You're correct in that normally using a where clause will break QVD optimisation. There is one exception to this though, which you could take advantage of here. This is when you use the EXISTS function.
In your case, you could load a simple inline table containing just the Name / ID of the country you want to load, then use EXISTS on your existing load.
For example:
tmpCountry:
LOAD * INLINE [
Country
UK
];
Data:
LOAD *
FROM [your qvd]
WHERE EXISTS (Country)
;
