We are closing the sale of our house next week. Our purchasers paid €5,000 at the 'sale agreed' stage and on signing contracts their solicitor asked our solicitor to see would we accept a further €20,000 as the contract deposit (it should have been over €40,000) and we accepted that as we know it is difficult (we had to borrow our own deposit for our new house from the credit union). Anyway basically I didn't care that it wasn't the full 10% once I knew it was a large enough figure to know they were committed.
I understand that you are nervous about them pulling out, but you can not let them have you over a barrel, you won't sleep until the contracts are signed and they will be in the driving seat the whole time. If I really wanted to buy a house I would get the deposit from somewhere (especially if you accept say €25,000) and believe me if they were in your shoes they would not accept €5,000. Don't listen to what estate agents say in relation to this, they are full of it and will say anything to get their commission, go with whatever your solicitor advises.