Services supplied the to Republic of Ireland / Romania
You need to determine the “place of supply” of the services. If the machines are a “fixture of the property that cannot be easily dismantled or moved”, the place of supply is where they are located (see section 7.4 of HMRC’s notice 749A). If the machines don’t meet this criteria, the general place of supply rules apply – which for B2B transactions are where the customer is located. So (assuming that your customers are all businesses) either way the services will be provided outside of the UK. They won’t be subject to UK VAT, and your customer will need to apply the reverse charge.
Selling goods to those countries
If you’re only considering the parts that you use in the process of installing / servicing the machines, they count as part of your supply of services rather than separate supplies of goods and are treated as above.
However if these goods are separate to the installation / servicing, you need to consider where they are at the time of sale. If they’re in the UK, you are making an export – you won’t charge UK VAT and import VAT will be due when the goods arrive in the foreign country. But if the goods are already abroad at the time of sale, you are making a supply of goods in that country and would need to register for VAT there.
Goods from Germany
The following HMRC guidance applies: https://www.gov.uk/guidance/vat-and-overseas-goods-sold-directly-to-customers-in-the-uk
For consignments under £135, assuming that the goods were outside the UK at the point of sale and you have provided the supplier with your VAT registration number, you can account for UK VAT using the reverse charge.