This weekend we went to a well know DIY store where my 4 year son was
determined to pick and buy a plant for Mummy with his own money

Any way he picked a Dwarf Rhododendron and we have neutral soil . He
heart would have been broken if we hadn't of bought it and the wife
wanted to try and plant it in the flower bed to replace a dead
Oestopernum.

We planted it adding ericaciuos soil in the hole. Will it thrive in
neutral soil with ericacious soil added or with it die or not flower ?

Also will the ericacious soil in the planting hole affect the other
plant around it which are not acid loving plants ?

Have a look around your area to see if there are rhododendrons growing in people's gardens, and that will give you a clue as to whether you will be disappointed. If you really have neutral soil, it is probably OK.

Even then, success depends on the variety. Some of the dwarf rhododendrons sold at this time of year are really "cut flowers", even though they are in a pot with soil. Intended to sit in your house looking pretty for a few weeks, not your garden: needs very green fingers to overwinter then and get them to flower again the next year.

If you have a proper garden variety of dwarf rhododendron, you will probably be OK provided it isn't an extreme acid loving variety. The main issue in keeping rhodies alive in can be giving them enough water, and they don't like the tap water if you live in a hard water area. But you can drown them if your soil is poorly drained, in which case you should have added some sand to your soil-ericaceous compost mix. When your water butt is empty after a long dry patch, then remember that they prefer tap water to no water at all. It is often a good idea to mulch them. They also need feeding with lime-free fertilisers.

It is unlikely the neighbouring plants will be bothered, unless they are extreme limestone-lovers.