If the budget is 0, don't do it!? Wait until commonsense prevails. If UK dwellings are paying £1400/y for gas and electricity, that's £28,000 over a 20 y period and any half-sensible country will at some point decide that part of this £28,000 should go into improved insulation/draughtproofing, not into heating the atmosphere.
TF external walls and masonry party walls are probably not that unusual. A lot of "CW" houses also have TF panels above and below the windows.