Our cot converted to a toddler bed too - worked well as it was all the same for DS. I have a friend who is converting theirs by taking off the side and stabilising it with bracing etc. Its one that doenst convert but they are changing it as they are not having any more kids and so buggering up a cot doesnt matter.

We got about 2 years use out of the toddler bed so well worth it for us (and two years as a cot so great for the money).