Work on fixed water and heating installations needs an autoriseret VVS-installatør (authorised plumbing contractor), or a firm that brings one. Ask which it is, and ask for that on the invoice (faktura). Authorisations are looked up at Sikkerhedsstyrelsen, sik.dk.
Næstved is the hub of South Zealand, with a centre and nearby villages. A drive out of town is common. Ask whether the quote includes that drive. The same 4 businesses as the Danish page: AADERUP VVS NÆSTVED ApS, AUT. VVS-INSTALLATØR V. JØRGENSEN A/S, LP VVS-TEKNIK ApS, T.O. Blikkenslager & Kobbersmed.