But there is an all-bus option with only two changes.
The X91 effectively runs non stop to somewhere near Silverstone, then non-stop to Towcester where it follows the standard hyper-wiggle via the town's housing estates; after which it runs non stop to Milton Keynes.
Presumably this was the cheapest way that the operator (Stagecoach) could respond to the level of developer funding on offer. Once the funding runs out the service will disappear with not a snowflake in the nether world chance of commercial success.
All the above products are for First Bus exclusive services.
** Actually somewhat less than 76. The TSY changes booklet separated out every route number and, clearly as with 81/82, some associated routes can occupy a single leaflet.