Harvey, I will be careful... won't wear heels but my flat boots!!
My next door neighbour had a mouse so she said but we think a rat...all the houses have connected underfloors, I put some peppermint oil in the air bricks...we didn't get a visitor...think you would need to keep the dogs away as I am not sure of the safety of the oil around dogs

Harvey - I did mention the other night that chocolate or pork fat are favoured baits for "Rattus Norwegicus". When placing traps they prefer to feed under cover or around the perimeter of an area enclosed or open. Leaning a board against the fence panels or the hedge will give them cover and encourage them to use it for cover etc. Be sure to leave sufficient room for the trap to close unhindered. Placing baited traps under cover will avoid the accidental injuring of small birds or other non target species.
Can't in all honesty recommend Griff's aromatherapy method of repulsion - I'd rather see the damn things dead. I do however know that peppermint oil won't damage your dogs - most of them hate the smell and will avoid it.
Hope this missive helps - be fer now G.

Harvey - Forgot to mention that rats are very neo-phobic so unless they are particularly stupid examples of their kind they will usually avoid any traps for the first three or so days.