There is no need to panic about your cholesterol being up - you don't know yet which bits of it are up and whether they are the good bits or the not as good bits. All the nurse will have looked at is the total, which is meaningless without the breakdown. Make sure you get a print out of the test results so you can see for yourself and analyse them at leisure. Also, was it a fasting test? If not, your triglycerides will have been raised especially if you had recently eaten something fatty.
As for blood pressure, this changes every minute or two depending on circumstances, and "white coat syndrome" plays a big part, as does stress. We are all stressed when having health checks, so this never helps. Even something silly like rushing to get to the surgery or waiting ages in the waiting room will have an effect. If this worries you, you could consider buying your own BP monitor so you can keep an eye on it at home. They are excellent tools, and not hugely expensive.