I will nip outside and have a look shortly before I pull bits off lol thanks for your advice though, I'll have to take a pic so one of you can circle the bit I need to pull off lol 
The first thing to check with a 1.8T that dont spool fast is the cam timing, just a tooth retard will eat all the low down power. The cam timing can be out because of poor fitting or the cam belt being stretched.
The next thing to remember is that your running the lower 95 ron map, which will have a lot less ignition advance and the peak load request (boost) will be a lot lower vs a map wrote for 98 fuel.
So by disconecting the N75 valve to allow the turbo to boost into oblivion is only really going to show you that there is more head room for boost, which I am 99% there will be. What yo need to do is find someone with vagcom who can log the requested/corrected and actual engine ms boost/load request and N75dc%, once you know what the ecu is asking for and how hard the hardware is working to meet the requested values, then you can start fault finding.
If you was running a map for the higher ron fuel then I would expect a huge kick of power down low along with some more risky advance, but a map for 95 ron IS going to be held back to reduce peak cylinder pressures.
Your only 35mins from us up the A444, If you give Pip a call on 01455 671233 and tell him Nick said book in for a quick logging session for free.. He will demand you bring hobnobs with you..lol
By having a logging session you will know whats going on and the way forward if any, so your not wasting your time trying to fix fault that aint there.
