I've had this before, but was never told there was a problem.
Also, if it was it a new container that the midwife gave you, sometimes there is a preservative in the container which is like little crystals. I had to do a complete 24 hour urine collection into a 5 litre bottle (or tanker perhaps?) recently and there was loads of the preservative and it did look weird (and the whole thing was a bit gross really!!!).
I was really surprised how often they expect you to use the same container. I had the same one all the way through my first pregnancy, and three quarters of the way through the second. They only gave me a new one when the old one started throwing protein readings out!!! I did wash it in between uses btw, but obviously not a medical sterilisation type thing. Isn't it lovely the things we have to do???
I recently noticed "bits" in mine, and results came back that I had a UTI. Obviously I dont know if the two are connected, but just wanted to reassure you that a UTI is not the end of the world - I had no symptoms, was given antibiotics for 7 days and told that as long as its treated promplty a UTI is not great cause for concern.
I would submit the sample with bits in, in case its important.