This is really much simpler than you are making out. The TT has double the battery capacity of the Hugo 1 because it literally has twice as many batteries ie 4 instead of two. Anyone in the UK can buy these batteries for less than £10 each. I doubt that it would take any techie more than 1 hour to replace them. I would have thought the labour cost for replacing four instead of two for Audio Sanctuary would be almost the same. So, you could do it yourself for say £40 all in, get it done by a local techie for maybe £100 all in or probably less than £200 by somewhere like Audio Sanctuary.
This ought to be more than enough info for you to decide whether to keep your TT or not. To pursue it further especially with a sense of outrage attached would seem unreasonable to me.
As far as I am aware these are the batteries.