Here in the US BestBuy's GeekSquad charges $19 USD, which is about 11 pounds, so the cost is normal. Now, the question of is it worth it is a little trickier. The dust and dirt build-up can clog the heatsink, fans, etc, resulting in an increased interior temperature that causes undue stress on your machine and the possible forced shutdown (newer computers) or burnup (older computers). Thus, it's pretty much a required preventative measure. While the cost they charge is considered standard, it's still quite high for what they're doing...removing the cover and using a fraction of a can of compressed air to clean it out before putting the cover back on. (It takes less than 15 minutes to do and costs less than a pound.) However, if you're uncomfortable doing it yourself it's a reasonable price to pay for the preventative maintenance.
Hope this helps,
John
P.S. I clean my computer out once a month, but every 6 months or so is generally recommended.
so yeah... my pc is full of dust n dirt. but im not good with pcs and i dont want 2 mess with my pc. i've asked a pro 2 do my pc...he say's it'll cost ten pound... is that worth it u reckon? cuz i really dnt wanna mess with the insides of my pc...asim no expert.

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