A bit of progress on this, I bought another LTE Lite 4/33C as spares/repair from eBay and got quite a bit more than I was expecting, instead of one I was sent two (intentionally! if you're on here, thanks again!!), complete with cases, both have 8mb expansion cards (the one I already had only had a 4mb card), both have working hard drives with Windows 95 installed, I'll be making backups of both in case I need any drivers/software from them.
Both floppy drives seem to have suffered the same fate as the one I already have, I've only opened one of the laptops so far and it appears to have the same stuck and sagging belt. Before I got the new laptops I already tried shortening the original belt but no matter how much shorter I make it, it never gets enough grip on the driven pulley, it will spin fine with no disk but as soon as any load is applied the belt stops and the motor keeps going! I've still had no luck finding a supplier of replacement belts, plenty for Amstrad and Spectrum but they are too wide and I don't know if the length is anywhere near the same, I think I'm going to order a couple anyway and try cutting them down to size.
In one of the cases that came with the new laptops there was a couple of pages from the manual, one just explains how to swap the battery, the other says you can put a sound card in the docking station to connect speakers, microphone, joystick and CD ROM drive, I have a few ISA sound cards so I'll put one in and see if I can get a CD drive to work. As for fitting a 3.5" floppy drive into the docking station, I've read about an adapter for 5.25" ribbon cables to fit a 3.5" floppy drive, although I can't seem to find where to get one, the only mention I've seen is that they used to come with 5.25" to 3.5" bay adapters, I've also seen ribbon cables with both types of connector but they all seem to have a 3.5" type connector on the motherboard end, I think my next plan here is to crimp a 3.5" connector onto the 5.25" ribbon cable in the dock and see how far that gets me!
On to the BIOS and different hard drives, I read about Maxtor Maxblast, from what I can gather it installs EZ BIOS to the hard drive to bypass the BIOS limitations, I'm not sure how this works, it was mentioned in regards to upgrading the hard drive in an LTE Lite so I assume it's exactly what I'm looking for, although now I have two working hard drives it's slipped closer to the bottom of the list.
Both new laptops have broken hinges, one worse than the other but neither as bad as the one I started with, it's a really bad design for laptop hinges, two captive nuts either side, pressed into the plastic lid right at the hinge, with all that leverage on thin plastic it's no wonder they break so easily. I plan to make some supports that run along the sides of the lid that the hinges screw to, much like modern laptop hinges, my plans involve using the milling machine but that's currently set up for something else I'm working on so I'm probably going to end up with the laptops staying in pieces for quite a while, although they're not in any way designed to be easy to work on so staying in pieces is probably best at least until I have a definitive solution to the floppy drives not working.
Seeing as I now have more laptops than I know what to do with I'm thinking about cutting the bottom out of the hard drive bay on one to allow easy assess to a CF card or maybe remove the floppy drive and have a CF card accessible from the floppy disk slot. I'd like to use a floppy emulator but with the original drives not using the standard connector I wouldn't know where to start, if anyone does know where to start I can take photos or could even send a physical drive for someone to poke at, I'm in UK but they're small and light so I don't mind international postage if required.