Really depends what you want out of one. I've had a mama's and papas classic one for 9 yrs ish and the only thing that's wearing is the bag it goes in and I've used it for 3 kids so far. Think about how often you will use it and from when. If you aren't going to use it for a newborn you don't need the bassinet bit. We first used ours at around 8 wks ish and didn't have the bassinet bit and it was fine. Randomly this was the first time she slept through. If it's occasional use you don't need to spend a fortune. We have also never bought an additional mattress, just used thick blankets under a sheet when they were tiny.
I wouldn't bother buying one until you need it. We have one that was given to us, rarely need to use it as hotels often provide a cot. For a small baby you can just take your own Moses basket with you. The expensive travel cots are a waste of money really unless it is going to get lots of use.
We got a cheap one (baby weavers) and a good folding mattress, which cost as much as the cot. It mostly stays at my mothers, as gets used a lot. It's now bring used by the 3rd and 4th grandchildren (not at the same time). No basinette.
Thanks! Guess will just use it at my mum's (although if I wait perhaps she'll buy one...!) and perhaps later on when camping?? But I forgot we'll be able to use the moses basket for a while so no rush.