rule of thumb is when car is still in maker warranty its better on one level as service history main dealer etc helps for any claims,, after warranty just find a long standing busy garage, as busy garages tend to be busy due to doing a good job could also look for the good garage scheme for good garages on their books, link below
The Good Garage Scheme: Good Garage Scheme – Car servicing, MOTs and car repairs
The Good Garage Scheme: Good Garage Scheme – Car servicing, MOTs and car repairs