^That's a little early for tourism imo - I will strongly recommend late april to late september..
In March it does at times reach 15C+ and the sun do shine from time to time ( last year march was really sunny ) but chances are most days will be fairly cloudy with 10-12C and cold nights.. ( technically it's "winter" ) on the positive side it's a time of year with little rain - compared to many other months of the year..
Few trees will have leafs at that time, but if you come late in the month ( as I will
strongly recommend if you do come at that time ) most of the spring flowers will be blossoming
Cold air and the risk of boring weather does ofcause not mean you can't have fun, but it's imo not the best time for a first time visit - and certainly not for a guy coming from Texas - unless you are ofcause trying to awoid getting sunburned
All that said if you do come promise to take a lot of pics - and just in case bring some sunglasses, I might just turn just as great as last march was - but with the changing weather and global warming there's no guarentees
BTW Job related or vacation? - if I remember right your HQ is in London right?