As the ISF notes, the majority of "Welfare" is targeted towards Pensioners
So of the £205 billion or so spent on tax credits and social security benefits about £111 billion is spent on those over pension age and £94 billion on those of working age.
Figure 1 and Table 1 show this breakdown of the 25% of total spending described as "welfare" by the government, alongside the 12% spent on state pensions. 4% goes on "personal social services", 3% on public service pensions, 4% on other benefits for pensioners, and the remaining 14% on benefits for those of working age.
What is welfare spending? - Institute For Fiscal Studies - IFS