Means testing for universal benefits for pensioners would be wrong. In part, because those pensioners have lived their lives and contributed to the state pot on the understanding that they would be in receipt of such benefits when they were eligible.
Although souunding superficially attractive, the idea of means testing wold fail the test of economics, too --- it would cost a signigicant amount of money to process all of the relevant documentation for the millions of recipients.
Having said all that....... there are a significant number of pensioners who are well off, and do not need free prescriptions, or a buss pass, or a free TV licence, come to that, and I dont see why there cannot be a process by which you could register an opt out for any of the benefits being offered - I cant see why that would cost a lot of money to implement, and I think quite a few wealthy recipients would quite happily opt out, to do their bit.