[combat1]

Anybody got an idea as to what its likely to cost to fix a tank into a vehicle to safety standard. thanks. 175 litre tank.

[concept]

Some will say ratchet straps are safe enough, and at that size/weight, it probably is, so to answer your question, not a lot.

If you require a cage, the cost of that plus fitting, probably a few hundred.

[Spruce]

Combat1 works out of any estate car so it may be slightly more difficult to answer as it depends on the back of the vehicle and how the tank will be positioned.

Where is the spare wheel (inside or underneath) and where is the fuel tank. Also what happens to the back seat? What about the rear footwells.

Most engineering business (small) will be able to help. The experts will be those who supply and fit small tipper bodies to Transit chassis cabs and other mods. Yellow pages is worth a look.
Phone a big dealership in your area that has a van sales section. The salesman should be able to suggest someone local. If not, a local van hire company will know who does van modifications and accessory fitting in your local area.

[combat1]

oh Spruce, you've given the game away! Combat works out of an estate car!
Before we start, Happy Christmas to you mate and thanks for the help you have given me.
I got fed up with barrels and they did my elbow in so invested in a 175 litre tank for the back of my astra estate. Its an upright tank and looks like a super tanker! put a dark blanket over it in transit in case plod takes a look.
The payload is well within the limits and it drives a little better when full.
Also invested in an electric sub pump and hose which fills the tank in about 5 mins, fantastic.
The last two days have been heaven, no lifting.
I use a 12v sub pump to transfer the water from the vehicle tank to the backpack.
The tank and all my kit fit into the bootwell, so the rear seats stay in place, with the seatbelts fastened.
I think stage one will be ratchet straps whilst I contact some of the people you suggested to discuss a more secure fixing. Ideally the option to fairly easily remove it would be useful for family stuff.
Hope you are ok and all the best.