I have worn shorts (get changed T the bedside), bra & a crop top bra thing over the top. Failing that, you could get a spaghetti strap vest, to go over the bra.
The will probably need to see you in the bra, and look at posture/spine from the front & behind.
I have always requested a female Physio & they have never questioned my request.
If you are asking your G.P for a referral and know which hospital it will be at, then you can ring the Physio Dept, speak to admin and request a female, they should put it on your notes.
If you self refer, by collecting and completing a form at the Physio Dept, then you can write 'female Therapist please' on the form yourself, although I don't think they will accept self referrals for neck & back.
I guess at the moment, due to restrictions that you may recieve a video call & talk to the Therapist that way.
You may have to wait around 6 weeks as well.
I hope you get it sorted.
P.S, some G.P surgeries have a Physio, if you didn't know & it should be on their website.