Dangerous goods advice- UK regs and ADR

Having had a time out break from H.G.V . driving class 2 only and only worked in delivering frozen food industry ive joined an agency and am currently working for and a local ish company my question is how much dangerous good can i transport on an 18 tonne 14 pallet wagon in layman terms please i.e how many 20 litre containers of oil or bleach
how many 50 litres drums of oil or chemicals
whats the limit on flammable items i can carry without an ADR
am i legal to carry a ibc container think theyre a 1000 litres, without an ADR ive tried looking online but its confusing , thank you for youre help