If you wanted to mark a special occasion or a one-off joke, you'd be far better investing yer money in getting a race named after your words of choice, either at horse racing (which will cost a biggish chunk of money, but get national coverage) or at yer local dog track, where it would cost you less than the radio ad - AND you'd get to present the prizes to the lucky winners. Prob get a free meal thrown in too as part of the package. Contact Hove dogs
I once had an advert for a pub in Guildford and they played it three times a day 1 peak time breakfast or drive home 1 mid peak afternoon or evening and 1 during the night and that was for 7 days and it was cheap. The down side that we got no reponse whatsoever to it other than existing customers saying they had heard it and speaking to other publicans they told me afterwards that advertisers on the radio only do it as a last resort if all else fails.
I looked into advertising on Splash FM a while ago.
As i recall the offer was something like a 20 second advert made and played at regular intervals throughout the day and occassionally at the weekend and evening depending on scheduling. It was a 12 month contract costing around £250 a month and there were also fringe benefits for supporting them but i didn't go for it so cant give you any definite numbers.
They were very happy to tal through possibilities and opions though so well worth looking into.
The more spots you buy the cheaper they get, and certain times of day are cheaper, obviously. Cheapest slots I've ever bought where the equivalent of £6 each for 30 second overnights on a middling sized local station.
10 seconds even in drive on a big station isn't going to cost hundreds let alone thousands per play.