sounds like having just moved in, you maybe should get the boiler a onceover from a serviceman, your pressure gain may just be the filling loop left open....make sure its closed and removed.
Release excess pressure by draining from bleed screw on a radiator (bit slow but works fine) bleed back to 1-1.5 bar when heating system is cold.
With the filling loop removed, if you find the pressure still goes up (with heating off) you may have a leak between your dhw and system water in your dhw heat exchanger and this will have to be replaced.
Or, if the pressure stays fine, the filling loop was the problem, and this leads me onto the dhw temp. problems your having, if the pressure goes up and the dhw heat exchager needs replacing, it would explain both problems, but if the pressure now stays as it should be, the dhw heat exchanger is crudded up with scale and sludge and may need replacing anyway.
(not a big job to replace them, should take 30-45mins max, don't be told its a huge job!)
T, June 2008