Oooo, exciting!
Lots to consider.
First and foremost - buying a home is a very emotional purchase. And you know what? It needs to be.
The biggest question to ask is at what price are you willing to max out at? Will you be shattered if you do not get the house? Has it taken a long time to find a house that you like as much as this? All things that are very important.
I know the process is slightly different in Scotland, but I'll give my England experience.
Estate agents.... <sigh>. It's so hard to know when they are lying and when they are being honest. Keep that in mind. They will likely tell you that lots of people are interested, etc., to create a false sense of urgency. Granted... there could be a lot of people interested!
Okay, real questions:
How long has the house been listed for?
Have they had any price reductions?
Have any other properties nearby sold recently? If so, what did they sell for?
Is there anything that needs "doing" to the property? This can be anything from a new roof and windows to ugly carpeting.
Questions to ask yourself but you don't need to disclose to me for privacy:
What is your financial position? Are you already approved in principle for a mortgage or a cash buyer? Are you putting down a solid down payment? These are all parts of the offer that can make you appeal more to the seller.
To answer your question, I think offering £170k for a £175k house is quite generous! BUT, it all goes back to that first paragraph of questions. It should be a solid offer that they would be unlikely to turn down!
Exciting times!