Problem With Shower Hot and Cold Water - What could be wrong? There is something wrong with my shower i'm not sure what. If...

There is something wrong with my shower i'm not sure what.

If you turn it on too quickly I shudders the pipes and it sounds similar to the house is caving in.

Then when the shower is running you capture bursts of hot water - Ok to stand under and consequently it runs really cold and this happens all shower.

Can any one suggest what could be wrong. I regard as I am going to have to get British Gas out but I don;t want to be fobbed bad.
Hi.. We Have Exactly duplicate problem! But we resolved it.. Mybe someone downstairs is Using the Taps. Because that effects the shower. Also when we turn ours on the lights flicker.. Does Yours Do the Same/? Sounds like a problem with the mixer tap on the shower. Get a plumber not British Gas if you don't want to get ripped off
It is a plumbing job. The shuddering might be an air block surrounded by the system. The hot and cold blasts are down to two things. Either the thermometer is on the blink, or somebody is running water or the washing domestic device somewhere else in the house! I lived with 4 men surrounded by a hostel and though the bathroom was off the kitchen and I would put up a sign that someone be in the shower they would fill their kettles and afterwards there would be exactly the problem you described.

Tell everyone that you are going to have a shower, and later tell them when you have finished!
Answers:    Apartment building? Single control valve for shower? Single control valve could indicate a malfunctioning mixing stopcock! New problem or has it been this opening for a length of time?;-)=
Don't win out British Gas its a plumbing problem. sounds like you have an nouns lock in the pipes- call a plumber