I have 4E 12 UK (13 US) sized 'plates of meat' and have the same problem with extra wide and high instep feet. I bought some size 13 UK (47 Euro), 'modern' waterproof side zip, short ankle high bike boots like yours Steve and had the same problem, so narrow and low instep I couldn't even get my foot in one. Gave them away.
I then bought the BMW 'Allround' boots in a Euro 48 (US 14) size to get the room. 'Made in Romania 06/2014', I just saw on the label. They have great reviews and are /were the economy entry level BMW boot for years but outsold and performed better than the flashier models according to many reviews. I got them discounted a fair bit. Side zips with Velcro locktabs on zip pulls to stop them unzipping, inner gusset with Velcroed storm flaps to keep out water. Instep flex panels, gusseted elastic calf expansion panels, ankle protection shields, replaceable soles and gear shift patches on both sides. Very high quality and waterproof.
I thought I was very happy with them after breaking in and short day rides but when I did my 3000km trip to the RDU and Brisbane I found them agony on right foot after a few hours due to a right small toe injury 30 years ago when a dislocated toe was found 12 months after a big accident and it was pinned but the pin bent and drifted about 2" into my foot and had to be surgically removed. The toe tendon was cut leaving it slightly cocked up. Might see if a bootmaker can stretch that area or cut and patch. Never had a problem with that foot until my recent long ride so back in leather Puma basketball type ankle boots around town.
I have quite a few pairs of work, military style, hiking and coldweather/snow boots but dislike laces on bike boots and some even with side zips look a bit weird riding (as I try to avoid the Clockwork Orange 'Bovver Boy' look), but may be brought into service for touring next time.
I would still recommend the BMW Allrounders for a wide high instep if you have no foot injurys.