Its all about the salmonella.
Shop eggs are no better than yours if they don't have the lion stamp.
What the Lion stamp means:
lion eggs
The risk of food poisoning from eggs is a combination of the presence of the salmonella in the first place and the levels of it if it is present. Levels of salmonella are lower the fresher they are and the cooler they are kept.
It is a bizarre quirk of the UK system that refrigerated eggs are classed as 'treated food' and cannot be sold as 'fresh' so all 'fresh' eggs have not been kept chilled even though that would make them safer.
Shop eggs will also have been longer from lay-to-lunch compared to yours, so any microbial life there was in them would have had longer to multiply, tho fewer of the eggs will be contaminated.
You can have your chickens vaccinated against salmonella which would bring them in line with the Lion stamped eggs from the shop.
So in summary Lion stamped shop eggs have very low incidence of salmonella but have more opportunity for any salmonella that was present to increase, while your eggs will be fresher but if not vaccinated will be more likely to be harbouring the bug in the first place.
So it is a bit tricky to say exactly which is safest without knowing how prevalent salmonella was in your hens.
To really trump the shop eggs you would vaccinate your hens and then your eggs would be the best there was for your mousses and ommelettes. 