I loved my Lima models... Have sold the majority but now only have 73s (which I'm attempting to fit Dapol chassis to), a 156 as it was my favourite from my first layout, and a 101 & HST in bits. Overall though I think the modern models are better
There is an excellent thread somewhere on improving the detail on the 73 chassis - loads to do which I couldn't face doing. After that I think the Lima 73 shape is excellent.
Not done one but the 31 looks good.
I'm quite a fan of vitrains 37s and 47s but they need alot of work to bring up to scratch
Enjoy your lima hacking though!!