Chalky soil is alkaline. Rhodies prefer a shady position in acid soil. You may get them to grow if you dig a load of peat into it but they will never look their best. And every so often you will have to supply more peat. A mulch of pine needles (which are acid) would also help.

If you are set on growing a rhododendron and have chalky/alkaline soil best to choose a very small one and grow in a large container. Filled with an ericaceous compost - preferably one that does not use peat as peat takes thousands of years to create. You need semi-shade and will need to keep well watered.

Certain species of rhododendron have been found growing on alkaine soil in parts of China. Research is currently being undertaken into these but they are not yet commercially available.
There are now one or two small cultivated rhodendrons that have been grown specifically for use in alkaline soils but I don't know much about them. The ones sold in Garden Centers are all acid loving plants.
Generally speaking, you need to follow the advice above.