going for a bloodtest in the morning to look at various issues, can i do a one hour ride to the surgery without any problems?

Yep.

Wouldn't count on the ride back though, depending how much they take

Maybe ask the people doing the bloodtest?

In a standard blood test they take two or three little test-tubes worth. It's not like donating blood where they take a pint. You'll be fine (if it's a standard blood test).

What Tom said, they won't take much blood.

three little test tubes! that's nearly a finger full.

yeah No worries
I cycle to the hospital once every 5-6 weeks to donate platelets
the nurses have never told me off for it yet