Minutes of a meeting of the STFC council held at the end of March report that if there is no improvement in the exchange-rate situation "there would be further pressure (on the budget) in the order of £43 million".
Options mooted to cover the deficit include considering whether any existing international subscriptions could be renegotiated "with the intention of reviewing them when sterling recovered" and looking at whether an element of the UK's subscriptions to Cern, the European particle physics centre, and other international projects could be paid in sterling, with the amount commensurate with that placed in sterling contracts.
The minutes of the STFC meeting can be found in that news story.
This isn't good news. At the time when the US, Japan, and China are putting extra money into science as part of their attempts to stimulate the economy, the UK (and also Canada) isn't doing the same. It will be interesting to see just what the ramifications of such action will be in later years.