Looking to upgrade central heating system

[Iwantmychairback]

This Summer. What do you recommend doing at the same time?
We live in a bungalow with a converted loft. Upstairs are 2 double bedrooms, each with a radiator and an en suite with no heating at all. These rooms are only used occasionally.
Downstairs is living room with 2 radiators, kitchen again with 2 radiators. These rooms are fine warmth wise. Bathroom is what used to be a double bedroom and has one radiator under the window. It’s always cold in here.
Hallway is warmest place in house with 2 small radiators and lobby has one small radiator.
Obviously I will be asking advice when getting quotes, but what did you do when replacing radiators? Or what do you wish you had done? Where would you put the thermostat? Any recommendations for warmest, most efficient make of radiator?

how old is your existing boiler?

you say the bathroom is cold. Is the existing radiator fully hot, all over?

What sort of timer and thermostat have you got?

You haven't got TRVs, have you?

The boiler is around 5 years old. It’s a Worcester. We are oil fired if that makes a difference.
The radiators are all very old and a lot of the heating controls (trv’s.????)no longer work. The bathroom radiator is on full and is warm all over.
Only timer/ thermostat we currently have is on the boiler itself.

"warm" all over does not sound hot enough.

The incoming pipe should be "too hot to hold" and the outgoing pipe should be "too hot to hold for long." You might be able to make it hotter by balancing the radiators.

You say your boiler is only 5 years old, so it will be a condensor and usually run rather less hot than an old iron boiler, so modern systems have larger radiators to give out equivalent heat. Often you can manage this by replacing a single with a double of the same length. A gas condensing boiler is at is most economical at around 60C but can be turned up in very cold weather to increase the output. I don't know about oil boilers.

I gather you do not have a room thermostat on the wall. This is waseful of energy and inefficient. You could start with that, it is an easy job and not disruptive like moving pipes. You can get a battery-operated wireless one, if you don't mind it going wrong more often than a wired one. Some can be operated by an app on your phone, if you like that sort of thing. Most modern ones can be adjusted to give different temperatures by time of day or day of week, which is very useful.

p.s.

Get a system filter which will trap circulating sludge and sediment on a magnet, if you don't already have one. This will reduce the risk of later blockages which can be very costly. It can be emptied of accumulated sludge about once a year and, when you know how, is no harder than emptying the dust out of a hoover.

Thanks for all that. I will mention the filter when asking for quotes.