Saving the odd copper is always a good idea. Well, nearly always. Decided to buy these cheap envelopes from a local oriental emporium (good name for it!).
Bit thin, I thought, but should do the job. Wrote the cards, popped them in the envelope, and then discovered the catch. No glue on the envelopes!
It was either get a Pritt stick or a messy session in the kitchen making flour and water paste! Duuuh. Worked out very economical!! You get what you pay for I suppose.