As a party wall surveyor I'd like to offer a few pointers which may help some of you:
1. Once you've made the decision to go ahead with a project, pop over to your neighbour's house with a bottle of wine and speak to your neighbours (NO EMAILS) as soon as possible, informing them of your decision. Explain that you're putting in for planning/permitted development and you intend to notify them under the Party Wall Act (using an experienced surveyor) so that both of you are protected under it. Make them feel comfortable that you are doing your best to do everything above board and want to minimise disruption. Remember, for most people, their house is their biggest asset so building works will naturally spook them.
Where neighbours don't communicate is when problems happen and neighbours are more likely to appoint their own surveyor. Keep an open line of communication and just be transparent about it.
Almost everyday we hear "my neighbour just sent me a party wall notice and I don't know what to do" or "I've never met them and I'd like to appoint a surveyor."
Don't sit behind the screen, be proactive and be neighbourly.
2. If you are going to appoint a party wall surveyor, try and find one who belongs to a body such as the Faculty of Party Wall Surveyors or the Pyramus and Thisbe Club, so that there is some sort of code of practice that they need to abide by, and make sure you ask them how they will mitigate costs, along with any other hidden fees. If they aren't transparent, forget it. If they aren't proactive, then expect delays in your project.
3. IF your neighbour decides to appoint their own surveyor, please be aware that they have probably received a handful of letters from party wall surveyors from all over the country marketing their services. These surveyors trawl the planning portal looking for people who are carrying out building works and then write to their neighbours informing them of their rights. Because there are low barriers to entry to become a party wall surveyor, you get some good surveyors but you get other surveyors who are all about their fees and charge extortionate amounts.
Ask your neighbour to get a surveyor from a party wall body, to make sure that they're local to the project (to avoid travelling expenses), to ensure they themselves aren't liable for any fees and most importantly...GOOGLE them.
4. If your neighbour does appoint a surveyor ask your surveyor to ask that surveyor for an indication of their fees, hourly rate and how long they think they'll spend on the project. Remember, you as the building owner are only down to pay reasonable fees. To give you an idea of how important it is to keep an eye on fees, I recently asked another party wall surveyor for his fee for a single storey rear extension. He came back to me with a fee of £2,250. We challenged this with one email and he quickly reduced it to £1,110.
There is a lot more I could write but I'm rushing out of the office, but happy to respond to specific questions.