Just having this issue now also with a booking for Jul with Lloyds Avios voucher. All these vouchers were due to expire on Oct 31st, I booked on 22nd giving me ticket validity to Oct 22nd this year - so no BA flights I can rebook onto.

Agent basically said policy is that they can't rebook on other carriers, and if they refund it then the voucher would expire. So basically zero options. I made the point that EU 261 entitles me to re-routing and doesn't make exceptions for Lloyds vouchers. The agent didn't explicitly agree with me but did say that she couldn't disagree after reading the EU's rules, so has gone to clarify with higher management and will call back tomorrow. All a bit of a nightmare.