Originally Posted by Post Scriptum

So quickly looking such itienary would yield something on hel-lhr-hel but lhr-cpt-lhr is just under 6k miles, so one should get 18k avios + scraps for hel-lhr-hel. But these seem costly.
one could fly via Doha a weekend run with just above 1k. This would yield (4600 miles doh-cpt) 13.5k + scraps so would look reasonable value for money.