can you buy condoms at self checkout and will i need id ? ?

Yes, you can buy condoms at self-checkout.  They're a non-Rx item as well as not being an item like sudafed or even canned air that can be used for nefarious purposes so, no, you don't need ID.
And simply a statement (not advocating for or against them) - Planned Parenthood gives them out for free or at low cost as well.

EDIT:  Just saw your update.  I was speaking to conditions within the U.S., don't know about UK protocols.