I am always struggling with pictures edges radio when I save they in Lightroom. Picture below shows sizes available in ASDA in Waterlooville in one hour service:
http://www.asda-photo.co.uk/ website is a bit useless and they do not say anything about sizes of photo prints in their stores.
Frames at ASDA are very expensive, quite cheap frames are available in nearby Wilco:
Edit: Tesco offers up to 40 x 60 photo prints for £40. Pictures can be uploaded in their machines in stores, everything over 20 x 30 (in this case 40 x 60) will be delivered to the local Tesco on next day. For strange reasons I can’t find 40 x 60 Tesco offer online on their website.