Seems to me that you should also have a competant electrician have a look at your board, ( what do you have ? the old wylex type ( fuses ) or a board with trips and an R.C.D. trip switch ) either way it sounds as if there may be a bad connection on a circuit. Is the pc on the same ring main ( socket loop ) as the tv ? if so this would re-inforce my suspicion of a bad \ loose wire IMHO
Just my two pence worth, and as stated, if you do go for a u.p.s. system back up. it need not be anything to big, hope this helps a bit
EDIT :- just as an after thought, it may be worth asking your electricity supplier if they have been doing an work \ changing any equipment etc etc
