Vauxhall Vectra water leaking into driver side footwell

For some time water has been leaking into driver side footwell. My partner knows a bit about cars and has removed the carpets. It's not clogged pollen filters or the heater/radiatior. We've finally found that it's coming in from a small weld under the steering column near the bonnet release catch but haven't a clue how it's actually getting in to that point. We feel if we seal this it will come in somewhere else. My partner thinks it will be a huge job and that the body work will need to be taken apart?!? would anyone have a clue what this could be/how to fix it before we end up with a huge garage bill? Thanks