Plumbing query; heating but no hot water.

[jaybird]

Background; I have a Ideal s24 mini boiler, sealed system, non combi, 3 story townhouse, hot water tank on ground floor and boiler on 1st floor.

I recently had 2 rads moved when getting work done on my house. I also just had the boiler serviced for the first time (been here nearly 3 years, new build). Now the problem; putting the heating on now, I have hot rads but no hot water. Bord gais engineer (did the service 2 days ago) says he thinks a blockage in the hot water system. Plumber involved in building work says nothing he did could have caused this problem. They moved 2 rads to nearby walls, and put the boiler pressure up to 2 bars from 1.5, saying this is more suitable for 3 story house (this makes sense as rads on top floor now properly hot, they never were before). Heating system had not been used since the spring, if that makes any difference.

Also boiler is now slowly dripping water onto my new solid oak worktop since service done.

Questions:
Any idea of the likely problem causing the lack of hot water?
Any idea of the likely cause? Is problem likely caused by the work done, the service, the lack of use in a while, or none of the above?
Is a DIY fix possible or advisable?
Who should I get to look at the problem (plumber from builders, BG man, AN Other?)
Does it sound costly to repair? What ball park figure am I looking at?
Anything I haven't thought of?


Any thoughts or advice greatly appreciated, we are having so many problems with the house I'm a little overwhelmed! (and completely broke!).