How do I install a shower to a megaflo

[Slugbabydotcom]

Firstly you cannot work on an unvented cylinder even if you own it unless you are qualified. If you make a mistake you can potentially make a bomb.

does connecting a shower mixer to an unvented hot water supply really require an unvented ticket ! where does the unvented cylinder finish and the hws pipework begin

The UDHW cardholders territory begins at the combination valve [which usually has the filter in it] and ends at the hot water outlet of the cylinder.
You can work on the hot water supply pipework that leads to your taps but to fit a balanced cold feed is off your patch.

I go along with gas4you's idea that theres a blocked filter somewhere.
Respect also to corgiman who pointed out that if your system is correctly fitted it should already have a balanced supply and ChrisR who implied it wont make much difference unless you had a mains pressure of over 3 bar.

Your megaflo should be tested every year by a UDHW man and it seems that his visit is already overdue. You can find your man HERE using the search terms plumbing and unvented cylinders along with your postcode