Two schools of thought.
1. No bother.
2. Oh heck - no margin for error.
I tend to go for number 2.
For number 1 to work there can be no hitches of any kind. Your purchaser must be certain that their funds will be in place at least a day or so before the agreed closing. No-one ( vendors, solicitors, purchasers) can get sick, be involved in an accident or have any personal difficulties ( small children or elderly parents needing emergency care). Removal people have to be organised and flexible - just in case. Searches have to be clear.
The sale should go through in the morning and then your solicitor can deal with the purchase. The same rules apply.
Anyone who has managed it will tell you its easy peasy. Anyone who has ever had the nightmare of anything going astray or wrong will tell you its a nightmare or crying children, sick cats in removal vans and solicitors getting increasingly fraught with out of control and stressed clients. My favourite is the screaming client who tells me " I don't care what you do, just close the deal" while you try to remind them that its not their money but the banks that they are spending and the fact that they "forgot" to organise their stamp duty IS a big issue!
So, all in all, not my favourite as it eats into the whole day as you try and track everything down. I personally advise clients to close their sale in advance so that they are not putting themselves under stress. But then they have to move out and store furniture in advance of buying. More stress.
mf