Scheduling a blood draw for a visiting relative

Problem: my parents are coming to visit me next week for 10 days.  My mother has just finished chemotherapy for her cancer, and her doctor's office is requesting that she have a blood sample taken while she's here to make sure her various nutrient/mineral/cell levels are not dangerously low.

When, how, and where can I get this done?  I know that it will likely have to be paid for since she's merely a visitor (and it would strictly be classified as non-emergency), but I don't even know WHERE to start.  A drop-in clinic would involve waiting for hours, but I want to find something we can just make an appointment for and then they fax the lab results back to her doctor's office in the US verifying that everything's okay.

Anyone been in this situation before?  What did you do?  Hospital?  GP?  NHS clinic?

When my aunt was here for my wedding, she hurt her thumb and it got infected. I phoned my local GP surgery and booked her in. They charged her for the services but that was fine.

Given she needs lab work, I'd phone well in advance to make sure they are ok to do it. Bear in mind, too, that lab results can take a while to get to you. Though cancer related ones may be faster (I'm waiting 3 weeks to see if my son has coeliac disease).

So they should take her, even though she's obviously not a registered patient?  I'm wondering what they would do, given that it's not an emergency (so they won't feel medically obliged to treat her).

I'll give them a call tomorrow, can't hurt to ask.

So they should take her, even though she's obviously not a registered patient?

She will have to fill a visitor's form at the doc's but it shouldn't be a problem.

My mother came and got a throat infection and she saw my local GP, I think she paid something like £21, but it was fine, she got antibiotics and she didn't have to pay anything (I don't think she did anyway)

Considering this a blood draw and NOT treatment for injury/illness, I think my best bet is to go to a diagnostic clinic (like the one Courtney works at!).  Their prices are reasonable, and since the testing is done in-house, we can get the results back very quickly.  Doing it at the GP would not be very timely, especially considering that if she IS ill, time is important.

Thanks for everyone's input!!  You've been very helpful.