LJT,
a one way is always cheaper. Even if its by only a couple of quid.
Following your post to ul, I have just checked a variety of airline direct booking websites and had the following result using a one-way departure date of 11 February and return of 25 March:
BA London - Lagos one way, £642 - return £446.30
Virgin Atlantic London - Lagos one way, 683.20 - return £507.80
Air France (same dates) Paris - Lagos one way €3481.76 - return €800.35
Lufthansa Frankfurt - Lagos one way £1762.80, - return £717.60
Bellview quoted $750 one way, but a one month economy class return at $849
That seems to comprehensively show that your checking is not very thorough - maybe you only looked at the Bellview site
