Low Flow & Pressure

[armstrongracer]

My bathroom basin (1st floor) has really bad flow and pressure which has developed over 3-4 months and its same on both circuits. When mixer on tap is cold only flow is same, move to hot, no change. Actually moving mixer from fully right to left doesn't change the flow at all. Basin is right next to a bath on same ring which has good flow & pressure for hot & cold and lifting the shower attachment high above the basin shows the whole circuit has adequate pressure. Also there is an on-suite non pumped shower & basin in the bedroom that have good flow and pressure. What confuses me is that generally when a tap starts to block pressure generally goes up but flow drops off, this has both being bad. Before I dismantle the tap any ideas as to what might be root cause.

 

[terryplumb]

Blocked filters ( if tap has any ,or on its supply pipes), kinked flexible tap connector hoses , or faulty valve within the tap.
I assume there are no isolation valves on the supplies to tap that may be partially closed ?