1 Speak to the manager
If the restaurant has failed to keep your booking ask to speak with the restaurant manager or owner and give them every opportunity to honour your booking; explain that if the booking isn’t honoured that you will be taking the matter further and claiming compensation.
2 If you're left out of pocket
If a table can’t be found then make reasonable efforts to find a suitable alternative restaurant.
If no comparable restaurant has space then make sure you keep any travel tickets or receipts so you can demonstrate to the restaurant how much you lost.
Send the restaurant owner or manager details of the costs that you are claiming and any receipts that you have, along with details of the attempts that you made to find an alternative restaurant.
3 If the booking was for a special occasion
If you’d booked the restaurant to celebrate a special occasion then you could ask for a reasonable sum for the disappointment and loss of enjoyment you had a result of the booking not being honoured.
But a word of warning, it's a good idea to think about these things from the perspective of a judge if the case was to go to court. While some judges may be prepared to make an award of this type others may be reluctant – the more significant the event the more likely an award would be.
The significance of the event could also affect the level of compensation the judge awards.
Whether or not the restaurant was on notice of the special occasion will also be a significant factor and it may be difficult to claim for a ruined silver anniversary celebration if the restaurant had no notice of the occasion. It is always a good idea to let the restaurant know what the occasion is when you book.
4 Last resort - small claims court
If you are not happy with the restaurant's response you could consider taking action against the restaurant in the small claims court.
There is a Pre-Action Protocol which sets out the steps you should go through before starting court action. Consider the value of the meal and disruption caused before taking your complaint to a small claims court. If the judge thinks the case is frivolous they could actually make a cost order against you if you lost.
If you are offered reimbursement of all your expense, such as travel, and unless the occasion spoilt was a particularly special one and you had made the restaurant aware of the occasion when you booked, then it is probably not advisable to go to court just to claim back the disappointment and loss of the enjoyment element.