P&o have two ships adults only all year round Arcadia & Artemis,have been on Arcadia twice,lovely ship.
P&O Arcadia and Artemis are adult only all the time
Saga operates all year round - if you are over 5.
Thomson Calpyso shi.
Some of the P&O cruise-liners are adult-only at all times - the P&O brochure details all this. And Saga cruises are over-50s at all times.
Spirit of Adventure caters for passengers over 21 only. I can thoroughly recommend this small ship.
Try P&O Arcadi.
P&O offer two Adult only ships all year round. Arcadia is a modern super-liner and although not as large was originally intended to be Cunard's Queen Victoria as a running mate for Queen Mary 2 focussing primarily on cruises. The second is Artemis which was originally part of the Princess Cruises fleet but was brought to the UK when the Victoria (Ex Sea Princess ex Kungsholm) was sold off. Artemis is small by super-liner standards. I haven't sailed on either of these but am a regular cruiser with P&O and would recommend them as a cruise line.
P&O cruises on Artemis and Arcadia are always child- fre.
We've just returned off a Fjords cruise on P&O Arcadia. No passengers allowed under 18 all year round - but we think that P&O are much too expensive for what you get overall.