Hi Annie,
In theory this is good and if he is buying via the UK banks then fine, but if he wants to raise money in Spain, the banks will not accept the company and he will have to purchase in his own name.
I assume the structure is uk ltd co ownes all shares of spanish SL (same as ltd) and the asset is the house. This isnt advised anymore as the authorites are aware of the tax avoidances. As your client buys the uk ltd company, there is no 7% purchase tax to pay, or notary fees, or lawyers fees as effectively the owner of the property is the same - the spanish SL.
One thing to check is the spanish SL doesnt have any liabilites or debts at all - a company search will show this, other than that there is no reason to do it
One word of advice - if the client is going to have to sell it on at a later stage, and the new buyer needs a mortgage, then your guy will be clobbered for taxes as the original price 'paid' will be shown on the title deeds, so the profit difference he will have to pay at a current rate of 18% of profit. If the property has been in the company for many years, then this could be huge! Bear in mind 99.9% of buyers will raise finance via a spanish bank and this will limit his selling possibilites if he insists on the company being purchased
He would be well advised to check out all the angles and then go for it if it ticks his boxes