Definitly not to young for a bed either a single or a toddler bed. our Ds2 was 16 months and went onto a single bed and Ds3 was 20 months and went into a toddler bed...

as for using a porta cot no problem there. A friend of mine used one from birth till just a few months ago with her daughter who was 2 in december, they had sold thier cot as their son was 5..