noticed one small thing which is slightly unusual and might potentially advance an identification.

where the stays meet the dropouts the seat stay is domed while the chainstay is blunt/open. usually a frame will exhibit the same detail here for both types of stays. you might wish to compare this to known frames of barbican heritage should you still suspect this marque.

seat binder is a gripfast which supports a british provenace.

keep in mind that braze-ons may be later additions so do not let them influence date estimates until more is known.