In fact Monty's garden is in the West Midlands, almost in Wales and gardens in the south are getting smaller with every new build crammed into tiny spaces. There are large gardens all over the country attached to older houses and terraces are the same up and down the country with tiny yards or gardens depending on which kind of worker the Victorians built them for.
That said, it is certainly true that Monty's style of gardening and planting is not immediately relevant to most ordinary gardeners and especially beginners and people looking for methods and ideas suited to smaller gardens and family life. However, there are things he does and plants he uses taht can be adpated for many gardens large and small. It just takes imagination and a bit of cnfidence and trial and error.
He does sow a lot of his plants too which is a good money saving ruse for any f-gardener but he also has teh space for all the different composts, the grit, the seed trays and potting benches which all makes it easy for him. Not so easy for those of us with smaller spaces and no greenhouse and, unnlike Geoff H, he doesn't show inventive things like GH's free or very cheap to make light box for seedlings and so on and so forth.
Beechgrove is a lot more practical and down to earth and fun too.