Photograph the layout, lift the trivets, caps and crowns, and soak the enamelled parts flat in a non-caustic degreaser. Spray cleaner onto the cloth rather than onto the hob, because on a freestanding Belling everything runs down onto the control fascia for the ovens below.
A Belling hob is usually the top of a range cooker rather than an appliance in its own right, and that changes both what you are cleaning and what you are risking.
It shares a fascia with the ovens
On a freestanding Belling the cooktop, the ovens and the grill share one control panel running the full width of the appliance. Every knob for every cavity sits on that fascia, directly beneath the hob.
So the single most useful habit on this appliance is to spray onto the cloth rather than onto the hob. Cleaner applied to the cooking surface runs downhill, across the fascia, and sits against printed markings and knob spindles. On an ordinary built-in hob that is a minor annoyance. On a range cooker it can leave you with an appliance whose controls are unreadable, and printed markings do not come back.
The same applies when you clean the ovens below: cleaner sprayed into a cavity runs out over the door edge and onto the fascia from the other direction. See how to clean a Belling oven.
The trivets run the full width
A Belling range hob carries cast iron trivets across 90cm or more, usually in several pieces, and they are heavier than the trivets on a built-in hob because they span a longer unsupported run.
Lift them off cold and lay them out in the order they came off, matching a photograph taken from directly above. On a wide hob the pieces are frequently not identical, particularly the ones flanking a central burner, and a trivet in the wrong position rocks under a pan.
Soak them flat for an hour in hot water with a non-caustic degreaser, in a tub lined with an old towel so the cast iron does not chip the porcelain, and work them with a stiff nylon brush rather than wire. Dry them by hand and immediately, because exposed iron rusts fast here.
Burner sizes, and the simmer that stops working
Belling hobs typically carry three or four burner sizes with caps and crowns matched to each. A large cap seated on a medium crown sits proud, the flame lifts off the ports, and that burner will not hold a low setting.
It presents as a gas problem and it is a reassembly problem. Clear the ports with a soft brush and a wooden toothpick, never a metal pin, since enlarging a port changes the gas-to-air mix permanently.
Glen Dimplex, and the Falcon connection
Belling and Falcon are the same group with Falcon above on price, and hob components frequently cross-reference between them. It is worth knowing when documentation for an older Belling is thin, and worth measuring rather than assuming.
What actually goes wrong
Faded fascia markings, from cleaner sprayed on the hob and allowed to run down.
Trivets returned to the wrong positions, so pans rock.
A burner that will not simmer, from a cap on the wrong crown.
Rusted cast iron, dried by air rather than by hand.
Should you do it yourself?
Do it yourself, lifting the trivets every month or two before anything sets hard, and keeping every product off the fascia.
Get someone in if the hob base under the burners has set solid, if a burner has become unreliable, or if you are having the ovens done anyway, which on a range cooker is usually the sensible way to do it.