I grow Rosa Warm Welcome (as a climber) don't know if it's available as a shrub. Slightly fragrant but nothing much to write home about.

Don't really know anything about roses, but a quick search gave this site which has lots of orange roses. The one (on page 2) called Wildfire is a small 2ft tall rose with medium fragrance apparently. They give you the type of scent from none to strongly scented.
I don't know anything about the company, so it's not a recommendation!
Copy and paste:
http://www.apuldramroses.co.uk/orange-Colour-Roses.htm

Or the Spalding rose co.

https://www.thefragrantrosecompany.co.uk/catalogsearch/result/?q=orange

Otherwise you could search for a rose in your Mother's name.

Have a look at the rose called Pat Austin, I bought a bare root one in spring and it has grown really well and I have masses of buds. Here is the description for David Austins website:-

This was an entirely new colour break in English Roses: a bright copper on the inside of the petals, with pale copper-yellow on the outer sides, creating a similar effect to ‘Austrian Copper’ (Rosa foetida ‘Bicolor’). The flowers are large and deeply cupped, the contrasting colours giving a most attractive effect. There is a strong Tea scent with a warm, sensuous background. ‘Pat Austin’ forms a large shrub with attractively glossy foliage. The blooms nod gracefully from the strong, elegantly arching growth, which is in proportion with the large flowers, showing them off to perfection. With its bright colouration, it is a wonderful rose for bringing excitement to a border of softer coloured roses and plants. Named after David Austin’s late wife, who was an accomplished sculptress.

that's really great, thank you everyone, I'll look into all of your suggestions!

Might I add a couple of others for you to consider?

Rosa 'Summer Song' - A David Austin Rose (Lovely scent)

Rosa 'Simply the Best' - A HT rose (Lightly scented)

That's great, many thanks I will look at those also, they all sound lovely!