I too built my own printer using a mismatch of parts / designs based on the mendelmax. I'm using 20mm square aluminium section to bolt it altogether. I think in total it's cost me just over £400.00 This includes everything.
the print head (hot end) I purchased cost me £40. It's called a J-Head and comes with a heat resistor and temprature sensor. It's got a 0.35mm hole. I am running a hotbed also.
I can give you as much info / help as you want regarding this. I print in both ABS and PLA which both require heating.
I am currently setting up http://www.3dbot.co.uk
which will have all the info on how to build my bot / designs / software sources etc. The site will be live very soon but I'm currently waiting for my provider to fix a setting in the server.. anyway
Let me know if you need more help :-)