Could still be something else but the backlights would be first check. The strips can be a pain to source sometimes, some engineers pinpoint the faulty ones and just replace them whereas ideally the whole bank should be replaced.
Your local tv repairman would probably charge 25-30 to look at the set and generally knock it off the bill if you accept their estimate. If it were the leds' then it is a total screen stripdown and handling a 47" screen single handed is no mean feat. They are extremely fragile when stripped down.
£150 may be enough but for 47" I would suggest that maybe the lower limit. Bigger the screen, the more leds' required. They can be a nightmare to remove as well.
Nothing to lose by enquiring mate except perhaps the inspection fee.