Welcome poppachris

I think what is being referred to with the Scalextric motors are the ones that are an open frame style of motor but are actually a sealed unit. You can still see the armature as it turns around, but you cannot disassemble it like an old X03/04 Tri-ang unit. Plenty of Hornby (and others including Powerline) engines used this type of motor. They generally involved a single worm drive to a drive axle.
Thomas and Duck have a Scalextric motor, Percy has a very cheap sealed can motor. The tender drive locos have a ring field unit, which is completely different,
They are not commonly in use any more.
Mine work well, like most of my locos, and don't give me any problems. Others may differ.
Cheers
Tony

 

Hi Chris

Think this is the type of thing your looking at.

http://www.hattons.co.uk/121925/Hornby_R9287_Thomas_and_Friends_0_6_0T_No_1_Thomas_the_Tank_Engine/StockDetail.aspx

The 'Scalextric-type' motor just means it's very similar (if not the same) as the motors in the Scalextric racing cars.

Might be difficult to run extremely slowly as they tend to go from stop to fairly fast once you apply the power.

Might not suite a hardened GWR branch line modeller, but for grandchildren it should be fine.

Ed