Shell, W-O Tankships, Northern Marine (Stena), Chevron..........all from their UK offices are looking for Engineers for tankers and even bunker barges. If you were up for LNG / LPG then NGSCo from Abu Dhabi are looking for people as well.
Not being a tanker man myself, I dont know of that many off hand, but I have seen the big players in the market, Chevron, Shell, BP, Mobil, advertising in the UK union paper Telegraph - yes I am still a member - on a regular basis. All the manning agencies have their adds in there as well.
If anybody is interested in the paper, it can be viewed from the web site www.nautilusuk.org
but unfortunately you have to be a member to view the job section.
I get the printed edition, so I dont mind looking if anybody has some specific enquireies.