This is a follow-on to the article that I wrote a while ago in regards to what 3D Printer I would recommend. I had a question about an entry level printer, in particular regarding kits, and thought I would add to my previous article.
My first recommendation would be that if you are going to build a kit...build a Prusa I3. This is by far the most popular type of kit and there will be a lot of support from other users.
The kit that I originally assembled is still available from 3D Printer Czar in China but the price ($499) is certainly not the lowest that can be found for a kit. In fact, and more on this in a bit, there are ready assembled I3's for that price. I am not sure what the "best" kit is at this point but if I were looking for the lowest cost Prusa I3 printer I would go to eBay and do a search for "Prusa I3 3D Printer Kit". I filtered the list by value to 100-500 quid to get rid of kit parts and checked the box for UK only stock. This yielded a list of printers from just over 100 GBP to the top end of 279 GBP.
I am not familiar with any of these kits but would advise spending some time reading the listing carefully and looking at customer reviews. I would recommend an aluminum frame for the extra sturdiness though my printer and its plastic frame worked just fine. I would probably not go with one of the very cheapest kits but if you are really strapped for cash it could be worth the risk. The worst case is that you may have to source an additional part or two from a range of readily available stock. I suspect, though I am not completely sure of this, but you are going to be on your own when it comes to doing the build in any case of these kits!
Building one of these inexpensive kits is going to be somewhat of a challenge and it is going to be a while before you print your first object. When you are finally printing it is going to take another chunk of time to get the printer tuned and calibrated so that prints are of good quality and can be done reliably. On the plus side...you will have learned a lot.
I am not sure that I would do it differently but there are some entry level printers out there now that I think would be worth considering. My particular favorite is the Wanhao Duplicator I3. This is a ready built Prusa I3 and while I do not have experience with it directly I did have a Wanhao Duplicator D4S and thought it was pretty well done. A ready to go printer, with the glass bed and a can of print bonding spray, will cost you 309 GBP. This is 100-150 quid more than a kit (with a metal frame) but you will be printing from day one.
There are some other entry level printers in a similar price range to the Wanhao that I describe above but I like the idea of the Prusa I3 as it is open source...if you want to upgrade it you will be able to do so. Some of the other entry level printers will not allow this as an option.
That is my two cents.