The older discs has AISIN written on them as does the box it came in. The Nav disc also contains the OS/firmware updates, not just map data, and that software would be written by AISIN.
If the Toyota disc is £200 then buy that. Around 2001 the company name stopped being written on the disc so they didn't have to produce two different ones, one for Lexus and another for Toyota - they are the same. However as you have a 2000 model you will have a 1st gen dvd unit and I don't think any Toyotas where sold with the full colour touch screen at that time (maybe the Amazon).