Any reason why your ditching spds ?. i get one fine with them even on long rides.
This! With the stiffness of modern shoe soles, the need to road clipless pedals has lessened. They might give a slightly lower stack height and slightly more stable platform but unless you're noticing hot-spots in your shoes it might not be worth the switch, especially as they come with the downside of waddling like a duck, slower engagement when starting off from junctions and Look cleats famous cheese-like build.
All that said, I have Shimano MTB SPDs on my MTB and cross bike and Look Keo on my road bike and am very happy with that setup.
As others have mentioned, DHB from Wiggle and Louis Garneau from Evans are good value and come in widths for actual humans and tend to give more for your money until you're looking north of £100. I use Specialised for both pedal types and am very happy with them. If you have any sort of instep issue I don't think you can beat Specialised. They have multiple insoles to tailor fit and a dedicated fitting process in their stores. Mavic, Sidi, Giro are all probably a bit too expensive and tend towards an Italian fit. Until I tried their shoes I didn't realise Italians only had 4 toes.