With that kind of budget, your best bet may be to approach the owners of under-used "excellent" domains and make them hefty offers, without even referring to traffic, revenue etc. In other words, find people sitting on superb generics that aren't doing anything at all with their domains (no parking, no site, nothing) and try and excite them with 5k-10k to part with the domain. Just don't make the mistake of asking them about traffic, as most likely they haven't even heard of domain parking or typeins and don't really understand the full value of the domains they had the foresight to register way-back-when...
It's quite a lot of effort, but you should be able to pick up at least once really good name for every 20-30 end-user owners you approach and go through a dialogue with.
It's also worth spending a bit of time familiarising yourself with the biggest players in the .co.uk namespace, as none of them are likely to sell their names cheaply. You're really looking for individuals/companies owning just 1 or 2 names, or perhaps a small handful, NOT domainers!