Ok, so the boiler's working. One of the problems is the lack of drop
to the boiler when the tank's near empty.

Looks like the oil was sucked to the level of the outlet, but there
wasn't enough head to displace the air when a couple of emergency
drums were thrown in, necessitating waiting for a partial fill & bleed
process.

So I want to move to a slimline tank, placed slightly higher up on
either a brick base, or some sort of blocks, probably on a concrete
over hardcore raft.

Is this DIY-able ? I'm happy with the concept of mixing and pouring
concrete, and building something that will hold a tank up, but.

1) What's the required thickness of raft to support a 60Kg tank plus
1000 litres of contents ?
2) what supporting should be put under the tank if any, I.e how many
legs and or cross supporting does it need ?
3) Any special considerations planning permission
4) Any statutory requirements siting or commissioning ?
5) I'm told a "recognised risk assessment undertaken by a competent
person" is required, Is it still required as the new tank will be
adjacent to the old one i'm decommissioning. So siting shouldn't be an
issue in the current location.
6) Pipework needs to be buried. Ok, with what protection and any
special considerations ? I'll probably connect the new tank pipework
to the old, existing pipework.
7) Any recommnedations as regards new filters/gate valves etc. Clearly
won't be reusing the existing items.

The tank i'm looking at is 160Cm long by 70 wide by 140 high.

Thanks,

Paul.