Mango got a reaction from Gunt in Where to get blood drawn?
It might still be difficult to find somewhere whilst covid is keeping clinics shut, but Superdrug and private cosmetic clinics usually have a nurse service you can book in with.
Medichecks used to list partner clinics on their website, might be worth a check.
Also, visiting phlebotomy services are available too. Google for your area.
Not free - £25-35 is roughly what I have paid various times.