Congratulations on your arrival! :-)
As for the basic items (t-shirts, shorts, etc.0), if you're looking for very inexpensive stuff, head straight to PRIMARK. They have the most inexpensive stuff I've seen. Burton's is also good for menswear.
Dress clothes....Marks and Spencer, of course. Littlewoods has a nice selection of shirts and ties...haven't really looked at their suits, etc.
Also, ASDA has some decent stuff as well. And definitely not expensive! I get my husband's dress shirts and ties from there fairly often and they hold up very very well.