Wiring plan for oak frame...

[sparkwright]

D-line trunking in various colours may even help.

 

[sparkwright]

Or a weatherproof switch outside somewhere...

 

[PBC_1966]

A not simple solution would be to use the door bell push to operate both door bell and a relay. A contact on the relay then triggers a timer to switch the light on for long enough to find the key and get the door open.

Or if there's already a bell push on the outside, would the physical arrangement permit going through the frame from there to a conventional light switch inside? If so, then you could use low-voltage relay switching but still have everything operate as a normal 2-way arrangement.

Depending upon existing routing and/or fixing of the bell wire, you might be able to use it to pull through something like 4-core thermostat wire or similar, or if stuck with 2-core bell wire some judicious use of a suitable power supply and diodes in combination with relay switching could allow the existing bell wire to serve both functions independently.

Personally, I'd always look for a hardwired solution before even thinking of going to any sort of wireless option.

 

[securespark]

I have such an SELV arrangement in the kid's bedrooms.

I have a din rail enclosure with a transformer and a relay in it.

The transformer goes down to 24V, used as the trigger circuit operated via PTM retractive switches.

I have MK 1 gang retractive switches by the doors and bell pushes by the beds.

In this case, the MK type switch would be indoors and a bell push mounted out in the porch on the end of a length of bellwire.

However, this arrangement would be difficult to retrofit to this installation as you would have to repurpose the switch wire in the hall as the 24V trigger and put a PTM switch on the end of it. Which may be tricky if it's a multi-gang switch.

 

[mattice]

Brilliant, some great ideas thanks. Trouble is I've become lazy and keep looking for standard off-the-shelf solutions. Perhaps I won't go as far as a photocell, trany, variable resistor, reed switch and a bit of bread board aka school electronics project... the main thing is usability, which is where the wireless options I've tried in the past have failed. Aesthetics are an equal first on this occasion.