My driveway (which is built with paving slabs) has been somewhat neglected
over the past year, and as a result has a major problem with weeds (some as
big as triffids ) growing up between the slabs. I'm planning on tackling
it in the near future, and wanted to get some advice.

My plan is as follows:

1. Remove the bigger clumps of weed
2. Lift the slabs
3. Put down some very strong weed killer
4. Check the level of the base (allowing for run-off) which I think is
currently just sand on hardcore.
5. Re-lay the slabs, and 'grout' them.

Any advice on what weedkiller to use, and the best (read easiest) way to
'grout' the slabs to stop anything growing back for as long as possible?

TIA

--
/Slugsie