New oil boiler - which one? Solar thermal too.

Becca22

Hi, moving into a property (2 bed, 1 bathroom bungalow) with oil, the previous owner passed away and her beneficiary decided (despite being told it was empty by a neighbour) to let the oil tank run dry. This has finished off the 12 year old regular oil boiler. Had some plumbers round and some say install external combi and others system boiler (some outside and some inside). What's people's experiences with each of these? Having an electric shower so it's only a bit of water for sinks. Safety/noise and other pros and cons of having it fitted outside over inside?

I'm hoping to have solar thermal installed as part of the Green Homes Grant so obviously the solar thermal company will install a cylinder for this (in the loft) The solar thermal companies say they can fit a special valve (look at Grant's Combisol) which works with a combi boiler and draws water from the solar cylinder or the combi depending on what the solar thermal has heated for that day.
My concern is bacteria and legionnaires with the solar thermal tank. In a system boiler set up the boiler would heat the cylinder up to a high temperature to kill bacteria? If I go for a combi and the solar heats the water in it's cylinder to 30-40'c and then this goes to the combi - will the combi kill this bacteria?

Anyone who has this set up or knows about it any advice would be appreciated!
Thanks in advance for your advice.