No clue about a registry. Have not heard of any planned baby showers (is that common in the UK?). We are Chinese, so normally gifts are given at the Full Moon, when the baby is a month old.
Cloth diapers....now that's an interesting idea. I will have to ask them if they plan to use disposable or cloth. My mom will go bananas if they decide to go cloth ROFL! It is pricey to start out...so might be a good thing. Like zsmom pointed out, there are so many styles though this might be difficult to give as a "surprise".
I am pretty sure they plan to nurse. A close cousin sells nursing covers and is a big nursing advocate so I know they would get lots of support. I nursed both of mine for a long time and would like to support that choice in any way I can. Was thinking of a really good quality nursing pillow. My cheap $20 Boppy did the job...but the $50-$60 ones really are worth it. Maybe a sling? I loved my sling - once I learned how to use it (which took until Baby #2 was 6 months old).
Or...maybe a nice rocking chair? I loved loved loved mine and used it constantly for the first year or so. Will have to find out if they have the space.
On a Mustachian note, I am super proud of my brother and SIL. They reported that they visited a kids yard sale and picked up 20 things!! Even better, I used to organize these huge kids yard sales in my neighborhood for years (earned a little extra pocket money as a SAHM) so the idea of used stuff for babies & kids is near and dear to my heart.