I was perusing the wares at the bottom of the 'steel' recycling skip at my local tip yesterday when my eye chanced upon one of these

I've been looking for a stainless boiler of about 45-50litres for a while now and being the cheapest of cheapskates I've been waiting for ebay to list one that none of my fellow homebrewers spot, so I can get it cheap. I have seen quite a few of these galvanised steel jobbies on ebay over the last 18 months or so and always dismissed them because they are galvanised steel. However the one I found turned out to be double skinned and the inner skin is stainless. Mine (I bought it obviously) has a capacity of 46.5 litres to the very top and it uses a standard burco butterfly element. Result!
I'm only mentioning it because if you are looking for a decent stainless tub to use as a boiler for 20-30l brews these look just the job, definitely worth checking out!
hth