+1 , the virtuoso is a cracking bike .I used to have one and it did sterling service till i upgraded .£100 sounds about right if you needed new shifters .The Carrera Virtuoso is a decent bike, although this is an older one. I ran a Virtuoso over the winter of 2011-12 and it was fine.
Should be OK but I'd personally be looking for a set of levers - if they're 7 speed see the For Sale section on here.
Sorry got these on ebay now not here... only starting at a tenner though (12 watchers!!!!)+1 , the virtuoso is a cracking bike .I used to have one and it did sterling service till i upgraded .£100 sounds about right if you needed new shifters .
@simon the viking has some at £25 if as @DCLane says has youur bike got a 7 gears at the back ?
All you need as well as the shifters are some cables + cable outerswith will probably set you back around £10