YonaL Your query is of a legal nature. The estate agent is a sales person who has no legal knowledge (or is not trained to have any legal knowledge). So, asking him about planned works is not something he will know about in the legal sense, Secondly, the estate agent is working for the seller to sell the property. Your solicitor is who you should be talking to.
During the course of the usual conveyancing for a leasehold property, the sellers would be expected to pay for and provide a leasehold/management pack, which would contain evidence of the service charge accounts for the previous three years, together with any details of any Section 20 notices served or any planned works which are not yet completed and/or paid for.
Your solicitor is right to ask for a retention for a possible shortfall in service charges for the current year, together with a suitable amount for any planned works which are due to go ahead. However, the sellers solicitors may agree a retention for a shortfall in service charges, but may argue that the future works which are planned will benefit you rather than the seller and therefore should be your responsibility. You could agree somewhere in the middle if the sellers are agreeable, or perhaps renegotiate the purchase price, but it is very much a negotiation between all of you.
If any retention is agreed, it will be held by the seller's solicitors and you would need to apply through your solicitor to request all or part of the retention either when a bill for the works is invoiced or when the final accounts for the current year are produced.
How many years remain on the. lease? The sellers can begin the process of extending the lease (assume they have owned for 2 years) but at your cost, or you can do this yourselves once you have owned for 2 years.
Not sure why you think the property market has crashed. As far as I am aware there are more properties coming onto the market and buyers are still buying and estate agents and conveyancers seem to be getting busier day by day.