You obviously know an unusual group of 67 year olds Bungled. The ones round here are spritely, spend their time travelling abroad in normal times, volunteering, walking and going to the gym etc. They would not like to be described as pensioners, although they may have just started taking their pensions.
I don't know why you say they are significantly at greater risk than group 6 who have wide ranging medical conditions. They are further up the order due to age and have been called first, but if they choose to wait that is up to them.
It sounds to me like your issue is with people having to travel generally. Perhaps you yourself will not be keen to travel to a mass centre when your turn comes? The reality is that it's not feasible to provide cpvaccination centres within 10 minutes or 10 miles of everyone to the capacity to cover the whole population and ensure they run at capacity. Again, this is about the big picture and not personal convenience.
Mass centres are needed to help get through the volume required. There can only be a certain number of these for viability purposes which means they won't be within 10 miles of everyone. But they allow more peoole to be vaccinated everyday and speed is of the essence. GPs couldn't run more local hubs and do their normal work too....extra capacity had to be brought in and flexible capacity to cover large geographical areas.
People haven't been barred from their local options, but it is clearly the case that if everyone wants to only attend locally, it will take twice as long to vaccinate the population. Therefore they are encouraged to attend their centre a distance away, when they are age groups 5, 7,8,9 are not in medical groups 4 or 6. Groups 5,7,8,9 are generally in good health. Many have cars and their without can use public transport or volunteer services to get there. Most see it as an outing. These groups 5,7,8,9 have not been required to shield and just maintain normal social distancing throughout the pandemic.
I think perhaps you have an issue with travelling for whatever reason. From a point of getting most peoole vaccinated as fast as possible, it entirely makes sense for age groups below 70 without medical issues (not group 6) to get done largely in the big centres which should be able to rattle through vast numbers very fast. It's all about large numbers being done fast.
Your perceptions of the state of 65-9s, ideas they have all been shielding and that they are at far greater risk which requires localised vaccination than those in Group 6 with identified medical clinical concerns all seems a bit odd to be honest.
When it's your turn, if you want the local vaccine, and if you're called by age group to the mass centre, well you won't be obliged to accept it. You can wait and be done locally,mbut will have to wait a bit longer. It will be your choice. You might choose based on just what's convenient for you, or think too about the bigger picture of getting through a very large population as fast as poss.