You choice of course, but given you were considering taking a £4k pay cut it seemed reasonable to assume you had sufficient money available. The rates of return are so extraordinarily high that it seems bonkers to ignore them, to the extent that even paying down debt is probably a worse option in the majority of cases. The ISA funds may be accessible as well I guess(?) were you to need to call on it.
Congratulations on the new job, btw
Congratulations on the new job, btw