Sorry to say if you want a zoom lens, 150 quid isn't going to get you much.
It depends if you want an IS lens or if you can live without it?
For example, a Canon EF-S50-250mm IS lens will set you back £180-£200.
This lens is very good value for money.
There are sigma non IS (not sure what their version of IS is called) 55-200mm or the 70-300mm lenses that fall within your budget.
Tamron also do a few within your budget as well.
If you can afford to save up a little bit money, I recommend the Canon 50-250mm IS lens.
Keep your kit lens and get a longer zoom lens and you'd still be able to go down to 18mm for wider shots.
You can have a look here for some prices:
www.camerabox.co.uk.
A lot depends on the range you want from the lens.