Why would you expect more?
> Facebook's European headquarters are in Dublin
So presumably all its billings are done from there. That would mean that the company had little or no earnings in the UK for it to be taxed on. However we still get a (tax) benefit from FB having an office in the UK, as it would have to pay N.I. employers contributions and its UK employees would pay UK income taxes - as well as VAT on all the stuff they bought with their wages.
This falls into the same category as people complaining that UK banks make "huge" profits - and therefore assuming that because the bank is based in the UK, all the vast profits come from UK customers. The joy of global businesses is that if you can attract them into your country's liberal, tax-friendly environment you can make many, many times more by taxing them on the income they make from foreign trading than a "fare share" policy would get, if they all buggered off to somewhere more sympathetic..