I have a Epi Dove and seen that you can get acoustic pickups like the one below for £44, they seem good as they just clip on to the acoustic hole. I have a couple of questions which are, if im playing effects through my amp, will these take effect if im playing the acoustic and 2) Are these sort of pickups worth it?
Can't really help much Kev except that Seymour Duncan are a premier pick up manufacturer and I have a few SD pick ups in my guitars and they are pretty good. SD woody pick ups are well known and well used.
£44.00 for a pick up sounds a bit pricey - I have done quick Google and you can get them cheaper - Hartnoll Guitars for one
Once you have attached the pick up and plugged it in it will act just like your electric so effects will work on your acoustic but an acoustic played through an electric guitar amp like your Blackstar HT5 will never sound quite right - it will sound more "electric" if you want.
Be careful of feedback because often acoustics amped up like this will feedback like a ba**ard
Acoustics are better amplified through a special acoustic amp which will give a purer less colored sound