The timing belt replacement interval was changed from 100,000 down to 60,000 miles, get it done VERY soon unless you have a lot of money to spend on a head rebuild. Remember to take into consideration that your car & belt is around 8 years old now.
The chance of using an air tool on the bottom pulley is very slim unless you wand to remove the rads of course.
£120 is IMO very reasonable for a timing belt kit whether it's Gates, Blueprint, or Toyota, (belt, idler & tensioner) & an uprated kevlar belt would cost near that on it's own.
There is a 'how to' guide on the forum, if you are doing it yourself.