When the women's retirement age was set at sixty, essentially no women worked sufficient contributing years to get a state pension, and those that did paid the reduced married women's stamp. By setting the age at about what was (in the 1920s) the typical age offset between men and their wives, it meant that men typically became eligible for the married man's pension as soon as they retired. As life expectancies were in the low seventies, what happened was people got the married man's pension for about five years, and then a widow's pension for a few more.
Today, more and more women are retiring with full pensions in their own name, and have a life expectancy of about 88.
UK population pyramid:
www.ons.gov.uk/ons/interactive/uk-population-pyramid---dvc1/index.html
There are about 12m people getting state pensions, and it currently costs about £100bn per year. Paying them £320 per week would cost about £200bn (I'll be generous and assume that you're stopping things like winter fuel payment in your new scheme). So you need to find another £100bn.
For comparison, the entire NHS budget is about £110bn, income tax brings in about £150bn and NI brings in about £110bn.
I once had a stand up row at a Labour Party meeting with a guy who claimed we could pay all pensioners £300 a week by not fighting "any more illegal wars" plus the usual rant about nuclear weapons.. I pointed out that the entire UK defence budget is only about £35bn, so if we closed down the entire military (I mean, the entire military, every ship, every plane, every soldier) his scheme would run out of money by about April. That made me a warmonger, apparently (no, me neither).
So, we could pay massively raised pensions by closing down the NHS. Another scheme would be doubling national insurance or nearly doubling income tax (say, basic rate 40%, higher rate 75%, something like that). Or we could close down the entire military and keep about a third of the NHS (say, close all GPs, all regional hospitals, keep a handful in big cities).
Essentially, with a working population of about 20m, you'd need to find a way to get £5000 out of each and every person.
Oh, and it's going to get a lot more expensive over the next twenty years.
www.theguardian.com/money/2013/dec/10/state-pensions-age-68