Hi there I have just come home from a hospital visit as my little guy has a head cold and was told to elevate his cot. Any suggestion how I would do this. Do I buy a sleeping wedge and place under the mattress ??

Red Nose recommends that baby is placed for sleep on their back on a firm, well-fitting & flat (not elevated) mattress.
This has been shown to be the safest position for all babies to be placed for sleep,
Babies who are elevated can wriggle under their bedding or roll into unsafe positions in their cot.

Elevating the cot can result in the baby sliding underneath the bedding and is not recommended. Pillows or positional devices that position the baby with an elevation and are often marketed for baby reflux, are not recommended due to the risks of suffocation and lack of evidence supporting efficacy.
https://rednose.org.au/article/why-back-to-sleep-is-the-safest-position-for-your-baby