Hi Clayre

simply something like

……………….reserves the right to lay you off without pay for up to ….. days in the event of any disruption to its business or any diminution in its requirements for work of the kind you are employed to undertake.

(If you don't specify number of days, a 'reasonable period' will be assumed. And there's a statutory limit / right to claim redundancy in response to long layoffs - see eg ACAS Layoffs and Short Time Working guidance,)

In reply to David:

Thanks David for the prompt reply. Much appreciated. Clayre