What scope for phonescoping on a budget less than £500 (1 Viewer)

Hi there guys my first on the forum, just venturing into phonescoping at the moment have a opticron hr 66 x27 fixed eyepiece and using a viking adapter with xperia xz2 compact. Looking to upgrade scope as its very old. Looking at ed/HD type but not sure on size of lens width from 50-80 but mm any opinions on all different sizes on the net, have looked at vanguard endeavour 80a but really not sure as others. Would be used for birding aswell.

From your location, I'd suggest heading on over to somewhere such as Cley Spy in Glandford and spending some time with them to test and try out new and secondhand models within your budget.
They can also advise on suitability for Phonescoping at the same time.

Trust this helps,
Dave