If you are looking at/viewing flats:
Preferably one with more than 80 years left on the lease. When viewing a property, ask the vendor how long is left on the lease - they may not know but if they do, it will save you from having to start the conveyancing process and then finding out further down the line that there is only 50 years left. You may be able to download a copy of the lease from Land Registry or get your solicitor to forward it to you as soon as they have it to hand. Then you can check the lease length.
First time buyers don't pay stamp duty on properties up to £300k, but £80 is below the threshold for stamp duty (£125k) even if you're not a first time buyer. If it is an additional property, then stamp duty would be 3%.
Service charges - ask the vendor what they pay/how often - it will give you an idea of how much you need to allow for this. My DS pays approx £50 per month for service charges (£600 per annum), but it does vary from property to property.
Read the Lease to find out what the ground rent charges are and if they double periodically. If the ground rent does double, how many years are there between the periodic rises.
Solicitor fees for a purchase may be approximately £700, and additional expenses may be Land Registry fees, search fees, mortgage administration fee and survey fees, depending on the type of survey you require.