the very first venusaur card from the base series? according to my issue of becket pokemon (issue 17, published in Jan 2001. the most recent issue i own lol), it's worth $35 and the first edition or if it is in mint condition, it's worth around $55. Don't know how much that is in pounds or euros though.
But the card is probably worth a lot more now. Back when this was published, a Charizard was worth $175 and it rose up to $300 in 2003, so I'll bet that card is worth quite a bit, especially since the pound greatly surpasses the dollar, does it not?