The £160 season last year covered absolutely everything. People could easily switch between different types of event and different venues.

If someone buys the Ham series ticket (I don't consider it a season) they still have to pay for morning workshops and the LNE, and at a price of £138 they will want to get full use from their ticket, therefore the Bedford concerts, Manor Pavillion and Blackmore Gardens events will loose potential customers.
In addition to the Ham series you could also pay for a £90 social dance ticket from Roy Godswen.

The unfortunate consequence of operating different events as separate profit centres is that the organisers will be competing for ticket sales to avoid their own losses. I suspect the use of venue-specific series tickets is an attempt to lock in a group of customers rather than provide a better service to the audience.
This is understandable from a financial standpoint, there is no cross-subsidy between events, and advance sales with provide upfront working capital for the organiser, but it does mean that the audience splits into separate distinct tribes instead of crossing between categories and experiencing something new.
I have always enjoyed the freedom to float between different types of concert, dance and session, and have the serendipity of stumbling across an unexpected delight.
I'd suggest ignoring the limitations of series tickets, and go to different events as the mood takes you.

alan J.