I got this for Christmas
http://amigakit.leamancomputing.com/catalog/product_info.php?cPath=21&products_id=438. Thank you Mrs AndyFC.
I had some problems getting my Amiga 1200 to mount the CD Rom - it wouldn't detect and IDEFix would crash (some incompatability with something on ClassicWB as running in safe mode allowed it to work), but I've used the atapi.device from idefix and used the mountlist from amicdfs2 and it all works great. The 3.5" HD is much faster than the 2.5" one it has replaced too.
So I now have a 2.5GB 3.5" drive and a CD Rom running from the internal IDE port, freeing up my PCMCIA slot for Ethernet (I already have a card which I have used before).
My next project is to get networking into my loft where the Amiga lives. I have a couple of options:
1) Powerline adapters
2) I also got a Raspberry Pi for Christmas so I could look into using that as the wireless receiver and using an Ethernet cable to link it to the Amiga.
In the new year I'm also getting an LCD screen - my in-laws have replaced their TV and I'm getting their old one - with SCART, composite and HDMI inputs.