you need an engine rebuild mate
plain and simple.
you might be lucky enough to get away with it only with the heads and gaskets, but usually its badly corroded heads or parished head gaskets that do the damage.
When not using the car for many years, the alloy corrodes and disolves, leaving behind nasty holes. When the car gets back on the road, and especially when it gets a few coolant flushes, it washes away all that disolved aluminium and leaves you with a small pores that might join the oil with the water, or water in the oil.
Check your dipstick. If its got "more oil" than it should, and it looks a bit soapy and white, then you've got water in the oil as well, which is worst.
If thats the case, the more you run it now, the more damage you are making.
Oil doesnt easily clean out from the radiator or inner walls of coolant hoses, so all the hoses should be replaced after repaired and radiator should be professionaly flushed and cleaned.
Sorry about the bad news mate, but if you can post a few pictures of your water tank and oil dipstick, we can be more sure. However, whatever the case, its not good news and it does cost to repair.