My 8 month old is very tall and strong and it won’t be long before we can climb out of his cot. Are toddler/ floor beds (which have normal single bed mattresses) safe?

Most babies do not attempt climbing from cot before 18mths of age.
There are a number of issues to consider when transferring any baby from cot to bed (regardless of age)
These include any access baby/toddler has to areas of the house that they would not have, if confined to a cot.

Have a look at the following links which explain the safest environment for a baby/toddler when transferring to a floor bed & how to mange this.
https://rednose.org.au/downloads/RN0407_22_Cot-to-Bed.pdf
https://rednose.org.au/article/making-your-home-safe-before-moving-a-child-from-a-cot-to-a-bed
https://rednose.org.au/article/where-to-sleep-a-child-who-has-moved-from-a-cot