CE mark tells you that the product conforms to EU environmental and safety regulations. Or rather, that the manufacturer CLAIMS that it does. It says nothing about test efficacy.
It might be 99% accurate (depending on what they mean by "accuracy" - usually this is true positive rate, but not always) when done by a trained lab tech. Certainly won't be when done at home. Accuracy also depends on how long after infection the test is done - too early and the false negative rate can be very high.
tl;dr don't trust that result as far as you can throw it.
I didn't buy the test with the intention of relying on it 100%. Although it may sound bizarre, I did it almost out of curiosity above anything else. I had an inkling that I
may have been exposed to the virus after a couple of trips into London on the Underground in very early March, so was curious to see what the result might be.
The stated accuracy rate was 98% one way and as good as 100% the other, one in terms of a positive, the other in terms of a negative (I can't remember which way round). But the overall accuracy was stated as 99%. This was at a time when previous antibody tests had recently been discredited, but newer, more reliable tests had become available. The research I went into at the time led me to believe my test was from the latter group. This was also borne out by the advertising on the Lloyds website at the time I bought my test.
Of course those figures those are based on 'perfect' collection of blood (eg by a trained haematologist) which certainly wouldn't apply to Joe Public doing a home test, with anywhere between dripping blood on the floor and mopping it up with a used tissue before squeezing out it into the vial - and cleaning and preparing the digit properly, before getting a steady flow of clean blood (a fast, continuous drip) with the use of the provided lancet(s) which came in individually sealed packets. Obviously my sample was the latter

. After getting a rather disappointing 'spot' of blood on my pinkie from one lancet, I proceeded to use the other two supplied which had me suddenly dripping fast and copiously, and filled the supplied vial in around 3s flat. I put the lid on and then spent 10mins cleaning up all the blood off the kitchen floor!
Perhaps my result wasn't the full 99% accurate, but I reckon it wasn't far off.