I try to get at least 2p value per Avios, and you won't get that by using for BoB (typical value 0.8 pence per Avios) and certainly not with part pay (typical value sub 0.7 pence per Avios, unless there is a special offer on).

The best way to get value - in my experience - is
- RFS, 2p value isn't difficult to get within Europe
- last minute domestic RFS if revenue fares are very high
- Gold Priority Rewards when caught out by very high fares (ski half term, some of the event periods in NCE or BCN). My greatest coup there was something like 7p per Avios.
- UuA particularly from WTP to CW. Probably for CW to First too, but that isn't something I do since I'd rather have the free upgrades.
- UuA from shorthaul N bucket to Club Europe
- Cathay flights particularly in Business
- One way tickets to and from North America, works best with IB flights from USA to Europe.