If you have a young family and are looking to book accommodation for a holiday or overnight stay, then you will need to consider the sleeping arrangements. If your child is still in a cot then you will need to make sure that there is going to be one available to you within the accommodation (this may be charged for) or that you take a travel cot with you. Another point to consider is if there is room to have a travel cot up in your room as this can cause a major issue and often parents have found themselves with nowhere to sleep or having to pay to upgrade their room to a bigger suite.
Most accommodation providers are more than happy to try and help you with your arrangements and will try and provide a cot if not the bedding too.
There is also a website that you can go on that has a list of child / baby friendly accommodation all over the UK, with reviews left by other parents on their experiences when staying in said place.