Among the exotics we've seen in our (UK) Berkshire garden are ring-necked parakeets (common hereabouts-large flocks roost in Richmond area, allegedly originally escapees from the set of a "Tarzan" type movie now naturalised), an African Grey parrot(managed to trace the owner via the local copshop but it flew away again before they could come for it)and some small birds that taxed my brain for days and all our bird books until I looked up a caged bird book in the library an found they were several types of zebra finch, obviously aviary escapees. Never came back, probably killed by UK winter or our local sparrow hawk. Most spectacular is the heron that often lands in our fairly small garden and has difficulty getting enough room to lift off again.
RtS