help with choosing lens

hi all ,
new to forums and need a little help . i own a canon eos 300d with lens kit , i also have a tamron af 28-300mm xr f3.5-6.3 ld (if) macro . i have a small budget of £400 and was looking at the canon ef 70-300mm f/4-5.6 is usm , does anyone have this lens and what do they think , i like taking pics of wildlife and was wandering if the canon lens will do , i know i dont have much of a budget but can anyone give me any advice as to which lens i could get with my £400 , all help much appreciated.
many thanks
dave

Hi Macca,

I have only just got my 350D at xmas, and I have been trawling on here for months before that, I wanted a good zoom lens and saw the Sigma 100-300 F4 (non DG version) which you can pick up for about £490.00, I hope to get this in a couple of months as it does have great reviews.

Mike

thanks mike ,
will have a look at that.
dave