Hi Clive. With mu code you'll be able to follow a twitterperson and show it's tweets. You can use it to find a word or hashtag in the tweet, but you'll have to change the code a little bit.
If you want the Arduino to do things, depending on the words after the hashtags, you'll have to add even more code.
If you're new to Arduino, this will not be easy, but don't give up, we all had to start somewhere.