I think what a lot of folks have missed is the fact that a lot of OFTEC regs are non enforceable.
OFTEC don't have the teeth like gas safe do,so you don't have to have a bunded tank yet unless,
the tank is in certain areas. The only real thing the enforces OFTEC regs is insurance companies.
But it's always best practise to do the best,yon can find out about tank regs online.Good luck Bob.
OFTEC are a trade association first and foremost who, amongst other things also run a competent persons scheme. They do not and have never set regulations as they have no authority to. What they do is collate the regulations set by Bristish Standards and Building Regulations, along with regional bylaws and requirements, manufacturers stipulations (to a degree) and industry codes of best practice, then as a registrant of that OFTEC scheme, you then adhere to those codes of practice.
What this means is, that any and all works done on an oil heating system MUST conform to BS5410 (parts 1 & 2) and Building Regulations at all times, anything less and you are breaking the law. It's also worth noting this applies if you are a member of a competent persons scheme or not, if you are a homeowner or tenant working on your home, or a mate helping someone out, it must always be to the prescribed standard. If you are ignorant of these standards you are not 'competent' in the legal sense.
So, as you will be aware, BS5410 part 1 2014 states all new installation or replacement fuel tanks MUST provide secondary containment to a set standard, it is no longer a regional bye law or dependent on minimum distances etc etc as before. Also, as they are classed as notifiable works they must be signed off by either a building control officer or an OFTEC registered person and then building control informed.
Please also note that secondary containment could be either a double skinned 'bunded' tank or a single skinned tank sited within a catch pit, both are permitted.
You are right in that OFTEC don't have the teeth that Gas Safe do but that is because Gas Safe is owned and ran by the HSE and they are organised and ran completely differently to an oil trade association. there are a few bodies that run competent person schemes for oil but OFTEC is the most well known whereas gas safe is the only one for gas.
Hope that clarifies things.