Looking for a small, decent quality, phone, for less than £200 [UK]

My GFs contract expires in March, and she wants to leave her shitty carrier (EE) and join me with Virgin, on one of their 30 day rolling 'contract' sim-only packages. As such she will need to buy a phone seperately. She currently has an Xperia SP I think, and is happy with the size of the phone but does not like it overall, its quite slow and buggy nowadays. While she will use it without a fuss when the EE contract expires, I want to buy her a replacement.

However I've had a hell of a time finding half decent ~4.5" phones. A couple of years back a Moto G would have done beautifully, now they seem to all be 5", which she definitely doesn't want due to the size of her hands.

I am looking for something that will perform for at least two years without breaking the bank. She wont use it for anything overly intensive, no HD movies or intensive games, mostly Reddit, Facebook, and music for commuting.

Thanks in advance!