We are part way through having the single jabs (first time round, not booster stage).
The hospital where I had it done (Breakspear) will give the booster shots or do the blood test to check for immunity.
They do say, however, that even if your LO has a blood test now and is shown to be immune to the diseases, this immunity is as at the current time and may not last her into adulthood.
IMO, it is best to get the boosters, especially as she is a girl and the immunity she will need against rubella is for her own pregnancies as an adult.
I have put a link to the hospital's info, I may not have been able to get it to the coorect page, but if you go to "Treatments", then "Individual MMR", then click on the booster section, you'll find it.
www.breakspearmedical.co.uk/