It’s certainly not a ring-topology, more hub and spoke, but even that doesn’t really describe it properly - basically, there is no redundancy, have a cable cut outside your home, have a drunk driver take out the street cabinet you are connected to, have an issue at the headend you are connected to, and it’s a case of ‘game over’!
On the other hand, you are paying a fraction of the cost that a business-class connection would be, how about a guaranteed 100 meg symmetric connection for £400 per month, except that they promise reconnection within 12 hours or proper compensation for loss of earnings!
As jpeg1 mentions above, this is a domestic internet connection, there is no SLA - theoretically you could be off line for months and all VM would be obliged is to pay you a little under £10 per day as compensation. By an interpretation of the rules, if you were off-line for over 30 days, then you could require VM to release you from contract without penalty and would be free to go elsewhere. Other than that.....